DISEASES

OF

THE HORSE’S FOOT

By

H. CAULTON REEKS

Fellow of the Royal College of Veterinary Surgeons Author of ‘The Common Colics
of the Horse’

1906

To

J. MacQueen, F.R.C.V.S.,

PROFESSOR OF SURGERY AT THE ROYAL VETERINARY COLLEGE, LONDON,
AS A SLIGHT ACKNOWLEDGMENT OF HIS ABILITY AS A TEACHER,
AND IN RETURN FOR MANY KINDLY SERVICES,
THIS VOLUME IS GRATEFULLY INSCRIBED BY

THE AUTHOR.

PREFACE

Stimulated by the reception accorded my ‘Common Colics of the Horse,’ both in this
country and in America, and assured by my publishers that a work on diseases of the
foot was needed, I have been led to give to the veterinary profession the present
volume.

While keeping the size of the book within reasonable limits, no effort has been
spared to render it as complete as possible. This has only been achieved by adding to
my own experience a great deal of the work of others. To mention individually those
who have given me permission to use their writings would be too long a matter here.
In every case, however, where the quotation is of any length, the source of my
information is given, either in the text or in an accompanying footnote. A few there
are who will, perhaps, find themselves quoted without my having first obtained their
permission to do so. They, with the others, will, I am sure, accept my hearty
thanks.

The publishers have been generous in the matter of illustrations and diagrams, and
although to the older practitioner some of these may appear superfluous, it is hoped
they will serve to render the work an acceptable textbook for the student.

H. CAULTON REEKS.

SPALDING, January, 1906.

CONTENTS

CHAPTER I

CHAPTER II

REGIONAL ANATOMY

• A. The Bones
• B. The Ligaments
• C. The Tendons
• D. The Arteries
• E. The Veins
• F. The Nerves
• G. The Complementary Apparatus of the Os Pedis
• H. The Keratogenous Membrane
• I. The Hoof

CHAPTER III

GENERAL PHYSIOLOGICAL AND ANATOMICAL OBSERVATIONS

• A. Development of the Hoof
• B. Chemical Properties and Histology of Horn
• C. Expansion and Contraction of the Hoof
• D. The Functions of the Lateral Cartilages
• E. Growth of the Hoof

CHAPTER IV

METHOD OF EXAMINING THE FOOT

CHAPTER V

GENERAL REMARKS ON OPERATIONS ON THE FOOT

• A. Methods of Restraint
• B. Instruments required
• C. The Application of Dressings
• D. Plantar Neurectomy
  • History of the Operation
  • Preparation of the Subject
  • The Operation
  • After-treatment
• E. Median Neurectomy
• F. Length of Rest after Neurectomy
• G. Sequelæ of Neurectomy
  • Liability of Pricked Foot going undetected
  • Loss of Tone in the Non-sensitive Area
  • Gelatinous Degeneration
  • Chronic Oedema of the Leg
  • Persistent Pruritus
  • Fracture of the Bones
  • Neuroma
  • Reunion of the Divided Nerve
  • The Existence of an Adventitious Nerve-supply
  • Stumbling
• H. Advantages of the Operation
• I. The Use of the Horse that has undergone Neurectomy

CHAPTER VI

FAULTY CONFORMATION

• A. Weak Heels
• B. Contracted Foot
  • (a) Contracted Heels
  • (b) Local or Coronary Contraction
• C. Flat-foot
• D. Pumiced-foot, Dropped Sole, or Convex Sole
• E. ‘Ringed’ or ‘Ribbed’ Hoof
• F. The Hoof with Bad Horn
  • (a) The Brittle Hoof
  • (b) The Spongy Hoof
• G. Club-Foot
• H. The Crooked Foot
  • (a) The Foot with Unequal Sides
  • (b) The Curved Hoof

CHAPTER VII

DISEASES ARISING FROM FAULTY CONFORMATION

• A. Sand-crack
  • Definition
  • Classification
  • Causes
  • Complications
  • Treatment
  • Surgical Shoeing for Sand-crack
• B. Corns
  • Definition
  • Classification
  • Causes
  • Pathological Anatomy and Histology
  • Treatment
  • Surgical Shoeing for Corn
• C. Chronic Bruised Sole

CHAPTER VIII

WOUNDS OF THE KERATOGENOUS MEMBRANE

• A. Nail-bound
  • Definition
  • Causes
  • Symptoms
  • Treatment
• B. Punctured Foot
  • Definition
  • Causes
  • Common Situations of the Wound
  • Classification
  • Symptoms and Diagnosis
  • Complications
  • Prognosis
  • Treatment
• C. Coronitis (Simple)
  • 1. Acute
    • Definition
    • Causes
    • Symptoms
    • Complications
    • Prognosis
    • Treatment
  • 2. Chronic
    • Definition
    • Causes
    • Symptoms
    • Treatment
• D. False Quarter
  • Definition
  • Causes
  • Treatment
• E. Accidental Tearing off of the Entire Hoof

CHAPTER IX

INFLAMMATORY AFFECTIONS OF THE KERATOGENOUS APPARATUS

• A. ACUTE
  • Acute Laminitis
    • Definition
    • Causes
    • Symptoms
    • Pathological Anatomy
    • Complications
    • Diagnosis and Prognosis
    • Treatment
    • Broad’s Treatment for Laminitis
    • Smith’s Operation for Laminitis
• B. CHRONIC
  • 1. Chronic Laminitis
    • Definition
    • Causes
    • Symptoms
    • Pathological Anatomy
    • Treatment
  • 2. Seedy-Toe
    • Definition
    • Causes
    • Symptoms
    • Treatment
  • 3. Keraphyllocele
    • Definition
    • Causes
    • Symptoms
    • Treatment
  • 4. Keratoma
  • 5. Thrush
    • Definition
    • Causes
    • Symptoms
    • Treatment
  • 6. Canker
    • Definition
    • Causes, Predisposing and Exciting
    • Symptoms and Pathological Anatomy
    • Differential Diagnosis and Prognosis
    • Treatment
    • Malcolm’s, Lieutenant Rose’s, Bermbach’s, Hoffmann’s and Imminger’s
      Treatment for Canker
  • 7. Specific Coronitis
    • Definition
    • Causes
    • Symptoms
    • Treatment

CHAPTER X

DISEASES OF THE LATERAL CARTILAGES

• A. Wounds Of The Cartilages
• B. Quittor
  • Definition
  • Classification
  • 1. Simple or Cutaneous Quittor
    • Definition
    • Causes
    • Symptoms
    • Pathological Anatomy
    • Prognosis
    • Complications
    • Treatment, Preventive and Curative
  • 2. Sub-horny Quittor
    • Definition
    • Causes
    • Symptoms and Diagnosis
    • Complications
    • Necrosis of the Lateral Cartilage
    • Pathological Anatomy of the Diseased Cartilage
    • Necrosis of Tendon and of Ligament
    • Ossification of the Cartilage
    • Treatment
    • Operations for Extirpation of the Cartilage
• C. Ossification of the Lateral Cartilages (Side-bones)
  • Definition
  • Symptoms and Diagnosis
  • Causes
  • Treatment
  • Smith’s Operation for Ossification of the Lateral Cartilages

CHAPTER XI

DISEASES OF THE BONES

• A. Periostitis and Ostitis
  • 1. Periostitis
    • (a) Simple Acute Periostitis
    • (b) Suppurative Periostitis
    • (c) Osteoplastic Periostitis
  • 2. Ostitis
    • (a) Rarefying Ostitis
    • (b) Osteoplastic Ostitis
    • (c) Caries and Necrosis
  • Treatment of Periostitis
  • Recorded Cases of Periostitis
• B. Pyramidal Disease, Buttress Foot, or Low Ringbone
  • Definition
  • Symptoms and Diagnosis
  • Pathological Anatomy
  • Treatment
  • Recorded Cases of Buttress Foot
• C. Fractures of the Bones
  • 1. Fractures of the Os Coronæ
    • Recorded Cases of Fractures of the Os Coronæ
  • 2. Fractures of the Os Pedis
    • Recorded Cases of Fractures of the Os Pedis
  • 3. Fractures of the Navicular Bone
    • Recorded Case of Fracture of the Navicular Bone
  • Treatment of Fractures of the Bones of the Foot

CHAPTER XII

DISEASES OF THE JOINTS

• A. Synovitis
  • (a) Simple
    • (1) Acute
    • (2) Chronic
  • (b) Purulent or Suppurative
• B. Arthritis
  • (a) Simple or Serous
  • (b) Acute
  • (c) Purulent or Suppurative
  • (d) Anchylosis
• C. Navicular Disease
  • Definition
  • History
  • Pathology
    • Changes in the Bursa
    • Changes in the Cartilage
    • Changes in the Tendon
    • Changes in the Bone
  • Causes
    • Heredity
    • Compression
    • Concussion
    • A Weak Navicular Bone
    • An Irregular Blood-supply to the Bone
    • Senile Decay
  • Symptoms and Diagnosis
  • Differential Diagnosis
  • Prognosis
  • Treatment
• D. Dislocations

LIST OF ILLUSTRATIONS

DISEASES OF THE HORSE’S FOOT

CHAPTER I

INTRODUCTION

The importance of that branch of veterinary surgery dealing with diseases of the
horse’s foot can hardly be overestimated. That the animal’s usefulness is dependent
upon his possession of four good feet is a fact that has long been recognised. Who,
indeed, is there to be found entirely unacquainted with one or other of such
well-known aphorisms as: ‘Whoever hath charge of a horse’s foot has the care of his
whole body’; ‘As well a horse with no head as a horse with no foot’; or the perhaps
better known, and certainly more epigrammatic, ‘No foot, no horse.’

Without taking these sayings literally, it will be admitted by almost everyone
that they contain a vast amount of actual truth. This allowed, it at once becomes
clear that a ready understanding of the diseases to which the foot is liable, the
means of holding them in check, and the correct methods of treating them should
figure largely in the knowledge at the command of the veterinary surgeon.

In the very great majority of instances the horse’s ability to perform labour is
the one thing that justifies his existence, and to that end the presence of four
good, sound feet is an almost indispensable qualification. And yet how many
circumstances do we see tending to militate against that one essential.

Even in colthood the foot, if neglected, may become a source of trouble. Unless
periodically examined and properly trimmed, its shape is liable to serious
alteration. From that in which it is best calculated to withstand the effects of the
wear it will be called upon to endure in after life, it may become so changed for the
worse as to seriously affect the animal’s value.

In the matter of feeding, too, trouble is likely to ensue. Particularly is this
the case where the colt shows points of exceptional merit. He is ‘got up’ for show,
and the feet are likely to fall victims to the mismanagement that frequent exhibition
so often carries with it. An extra allowance of peas, beans, wheat, or other equally
injurious food is given. The result is a severe attack of laminitis, and an otherwise
valuable and promising colt is permanently ruined.

Exposed as it is, too, to injury, the foot of a young horse, even at grass, is
frequently the seat of injuries from picked up nails, stakes, or other agents which,
unless detected and carefully treated, may terminate in a troublesome case of quittor
and incurable lameness.

With the passing of colthood, and the coming into effect of the evils of further
domestication, the troubles to which the foot is open become more numerous. Foremost
among them will come those having their starting-point in errors of practice
originating in the forge; for, in spite of attempts at their education, smiths, as a
class, are as yet grievously unversed in even the elementary knowledge of the
delicate construction of the member that is entrusted to their care.

This fact has been dilated on in books devoted to shoeing, and in the prefatory
note to the last edition of Fleming’s manual on this subject we find the following
statement: ‘The records of all humane societies show that, of prosecutions for
cruelty to animals, an overwhelming majority refer to the horse; and of these, a
large proportion are for working horses while suffering from lameness in one form or
other.

‘So frequent are such cases that observers have concluded that their prevalence
must result from some specific cause, and, not unnaturally, attention has thus been
directed to the various modes of management practised in relation to the horse’s
foot, to the manner of shoeing, and, in particular, to the way in which the foot is
prepared for the shoe.’

It must be remembered, however, that although harm in the forge may frequently
arise from culpable roughness or carelessness, such is not necessarily always the
case, and that quite as much injury may result from careful and conscientious
workmanship when it is unfortunate enough to be based upon principles wrong in
themselves to commence with.

It so happens, too, that shoeing, in itself a necessary evil, may be responsible
for injuries in the causation of which the smith can have played no part. Take, for
example, the ill effects following upon the animal’s attendant allowing him to carry
his shoes for too long a time. In this case the natural growth of the horn carries
the heel of the shoe further beneath the foot than is safe for a correct bearing; in
fact, anterior to the point of inflection of the wall. The shoe, at the same time, is
greatly thinned from excessive wear. Result, a sharp and easily-bended piece of iron
situate immediately under the seat of corn. Pressure or actual cutting of the sole is
bound to occur, and the animal is lamed.

Again, apart from the question of negligence or otherwise on the part of the smith
or the animal’s attendant, it must be remembered that the nailing on to the foot of a
plate of iron is not giving to the animal an easier means of progression. The reverse
is the case. In place of the sucker-like face of the natural horn is substituted a
smooth, and, with wear, highly-polished surface. Slipping and sliding attempts to
gain a foothold become frequent, and strains of the tendons and ligaments follow in
their wake.

As, however, this treatise is not intended to deal with the art of shoeing, the
reader must be referred to other works for further information. In addition to
Fleming’s, there may be mentioned, among others, Hunting’s ‘Art of Horse Shoeing,’
and the very excellent volume of Messrs. Dollar and Wheatley on the same subject.
Leaving the forge, we may next look to the nature of the animal’s work, and the
conditions under which he is kept, for active causes in the production of disorders
of the foot. From the yielding softness of the pasture he is called to spend the bulk
of his time upon the hard macadamized tracks of our country roads, or the still more
hard and more dangerous asphalt pavings or granite sets of our towns. The former,
with the bruises they will give the sole and frog from loose and scattered stones,
and the latter, with the increased concussion they will entail on the limb, are
active factors in the troubles with which we are about to deal. Upon these unyielding
surfaces the horse is called to carry slowly or rapidly, as the case may be, not only
his own weight, but, in addition, is asked to labour at the hauling of heavy loads.
The effects of concussion and heavy traction combined are bound primarily to find the
feet, and such diseases as side-bones, ringbones, corns, and sand-cracks commence to
make their appearance.

Again, as opposed to the comparative healthiness of the surroundings when at
grass, consideration must be given to the chemical changes the foot is frequently
subjected to when the animal is housed.

Only too often the bedding the animal has to stand upon for several hours of the
twenty-four can only be fitly described as ‘filthy in the extreme.’ The ammoniacal
exhalations from these collected body-discharges must, and do, have a prejudicial
effect upon the nature of the horn, and, though slow in its progress, mischief is
bound sooner or later to occur in the shape of a weakened and discharging frog, with
its concomitant of contracted heels. Lucky it is in such a case if canker does not
follow on.

Observers, too, have chronicled the occurrence in horse’s feet of disease
resulting from the use of moss litter. Tenderness in the foot is first noticeable,
which tenderness is afterwards followed by a peculiar softening of the horn of the
sole and the frog. What should be a dense, fairly resilient substance is transformed
into a material affording a yielding sensation to the fingers not unlike that
imparted by a soft indiarubber, and as easily sliced as cheese-rind.

Lastly, though the foot is extremely liable to suffer from the effects of extreme
dryness or excessive humidity, especially with regard to the changes thus brought
about in the nature of the horn, it is perforce exposed at all times to the varying
condition of the roads upon which it must travel. The intense dryness of summer and
the constant damp of winter, each in their turn take part in the deteriorating
influences at work upon it.

Though this subject might be indefinitely prolonged, this brief
résumé of the adverse circumstances to which the foot of the horse is
exposed is sufficient to point out the extreme importance of its study to the
veterinary surgeon. So long as the horse is used as a beast of burden so long will
this branch of veterinary surgery offer a wide and remunerative field of labour.

CHAPTER II

REGIONAL ANATOMY

Considered from a zoological standpoint, the foot of the horse will include all
those parts from the knee and hock downwards. For the purposes of this treatise,
however, the word foot will be used in its more popular sense, and will refer solely
to those portions of the digit contained within the hoof. When, in this chapter on
regional anatomy, or elsewhere, the descriptive matter or the illustrations exceed
that limit, it will be with the object of observing the relationship between the
parts we are concerned with and adjoining structures.

Taking the limit we have set, and enumerating the parts within the hoof from
within outwards, we find them as follows:

A. THE BONES.—The lower portion of the second phalanx or os coronæ;
the third phalanx, os pedis, or coffin bone; and the navicular or shuttle bone.

B. THE LIGAMENTS.—The ligaments binding the articulation.

C. THE TENDONS.—The terminal portions of the extensor pedis and the flexor
perforans.

D. THE ARTERIES.

E. THE VEINS.

F. THE NERVES.

G. THE COMPLEMENTARY APPARATUS OF THE OS PEDIS.

H. THE KERATOGENOUS MEMBRANE.

I. THE HOOF.

A. THE BONES.

THE SECOND PHALANX, OS CORONÆ, OR SMALL PASTERN BONE.—;This belongs to
the class of small bones, in that it possesses no medullary canal. It is situated
obliquely in the digit, running from above downwards and from behind to before, and
articulating superiorly with the first phalanx or os suffraginis, and inferiorly with
the third phalanx and the navicular bone.

FIG. 1.—THE BONES OF THE PHALANX. 1, The os suffraginis; 2, the os
coronæ; 3, the os pedis; 4, the navicular bone, hidden by the wing of the os
pedis, is in articulation in the position indicated by the barbed line.

FIG. 2.—SECOND PHALANX OR OS CORONÆ (ANTERIOR VIEW). 1, Anterior
surface; 2, superior articulatory surface; 3, inferior articulatory surface; 4, pits
for ligamentous attachment.

FIG. 3.—SECOND PHALANX OR OS CORONÆ (POSTERIOR VIEW). 1, Posterior
surface; 2, gliding surface for passage of flexor perforans; 3, lower articulatory
surface.

Cubical in shape, it is flattened from before to behind, and may be described as
possessing six surfaces: An anterior surface, covered with slight imprints;
a posterior surface, provided above with a transversely elongated gliding
surface for the passage of the flexor perforans; two lateral surfaces, each
rough and perforated by foraminæ, and each bearing on its lower portion a
thumb-like imprint for ligamentous attachment, and for the insertion of the bifid
extremity of the perforatus tendon; a superior surface, bearing two shallow
articular cavities, separated by an antero-posterior ridge, for the accommodation of
the lower articulating surface of the first phalanx; an inferior surface, also
articulatory, which in shape is obverse to the superior, bearing two unequal
condyles, separated by an ill-defined antero-posterior groove, which surface
articulates with the os pedis and the navicular bone.

Development.—The bone usually ossifies from one centre, but often
there is a complementary nucleus for the upper surface.

THE THIRD PHALANX, OS PEDIS, OR COFFIN BONE.—This also belongs to the class
of short bones. It forms the termination of the digit, and, with the navicular bone,
is included entirely within the hoof. For our examination it offers three
surfaces, two lateral angles, and three edges.

The Anterior or Laminal Surface, following closely in contour the wall of
the hoof, is markedly convex from side to side, nearly straight from above to below,
and closely dotted with foraminæ of varying sizes. On each side of this surface
is to be seen a distinct groove, the preplantar groove, or preplantar
fissure, which, commencing behind, between the basilar and retrossal processes,
runs horizontally forwards from the angles or wings of the bone, and terminates
anteriorly in one of the larger foraminæ. As the name ‘laminal’ indicates, it
is this surface which in the fresh state is covered by the sensitive
laminæ.

The Inferior or Plantar Surface, hollowed in the form of a low arch,
presents for our inspection two regions, an anterior and a posterior, divided by a
well-marked line, the Semilunar Crest, which extends forward in the shape of a
semicircle. The anterior region, as is the laminal surface, is covered with
foraminæ; in this case more minute. In the recent state it is covered by the
sensitive sole. The posterior region, lying immediately behind the semilunar crest,
shows on each side of a median process a large foramen, the Plantar Foramen.
From this foramen runs the Plantar Groove, a channel, bounded above by the
superior edge, and below by the semilunar crest of the bone, which conducts the
plantar arteries into the Semilunar Sinus, a well-marked cavity in the
interior of the bone.

The Superior or Articular Surface consists of two shallow depressions,
divided by a slight median ridge. Its posterior part shows a transversely elongated
facet for articulation with the navicular bone.

The Superior Edge, outlining the superior margin of the laminal surface,
describes a curve, with the convexity of the curve forward. In the centre of the
curve is a triangular process, the Pyramidal Process, which serves as the
point of attachment of the extensor pedis.

The Inferior Edge, the most extensive of the three, separates the laminal
from the solar surface. It is semicircular in shape, sharp, and finely dentated, and
is perforated by eight to ten large foraminæ.

The Posterior Edge, very slightly concave, divides the small, transversely
elongated facet of the superior surface from the posterior region of the inferior
surface.

The Lateral Angles of the bone, also termed the Wings, are two
projections directed backwards. Each is divided by a cleft into an upper, the
Basilar Process, and a lower, the Retrossal Process. In old animals the
posterior portion of the cleft separating the two processes gradually becomes filled
in with bony deposit, thus transforming the cleft into a foramen, which gives passage
to the preplantar artery. We may mention in passing that the lateral angles give
attachment to the lateral fibro-cartilages, and that the lateral angles themselves in
old horses become increased in size owing to ossification of portions of the adjacent
lateral cartilages.

Development.—The os pedis ossifies from two centres, one of which is
for the articular surface; but this epiphysis fuses with the rest of the bone before
birth.

FIG. 4.—THIRD PHALANX OR OS PEDIS (POSTERO-LATERAL VIEW). 1, Anterior or
laminal surface; 2, preplantar foramen; 3, preplantar groove; 4, basilar process of
the wing; 5, retrossal process of the wing; 6, foramen caused by the ossifying
together posteriorly of the basilar and retrossal processes.

FIG. 5.—THIRD PHALANX OR OS PEDIS (VIEWED FROM BELOW). 1, Plantar surface;
2, plantar foramen and plantar groove; 3, semilunar crest; 4, tendinous surface; 5,
retrossal processes of the wings.

THE NAVICULAR BONE, SHUTTLE BONE, OR SMALL SESAMOID.—Placed behind the
articulating point of the second and third phalanges, this small shuttle-shaped bone
assists in the formation of the pedal articulation. It is elongated transversely,
flattened from above to below, and narrow at its extremities. In it we see two
surfaces, and two borders.

The Superior or Articular Surface of the bone, which may easily be
recognised by its smoothness, is moulded upon the lower articular surface of the
second phalanx, being convex in its middle, and concave on either side.

The Inferior or Tendinous Surface resembles the preceding in form, but is
broader and less smooth. In the recent state it is covered with fibro-cartilage for
the passage of the flexor perforans. The Anterior Border possesses above a
small transversely elongated facet for articulation with the os pedis, and below a
more extensive grooved portion, perforated by numerous foraminæ, affording
attachment to the interosseous ligaments of the articulation. The Posterior
Border, thick in the middle, but thinner towards the extremities, is roughened
for ligamentous attachment. Development.—The bone ossifies from a single
centre.

B. THE LIGAMENTS.

THE ARTICULATION OF THE FIRST WITH THE SECOND PHALANX, OR THE PASTERN
JOINT.—Adhering to the limit we have set, this articulation should not receive
our attention. As, however, we shall in a later page be concerned with fractures of
the os coronæ, which fractures may affect the articulation above mentioned, a
brief note of its formation will not be out of place.

It is an imperfect hinge-joint, permitting of extension and flexion, allowing the
first phalanx to pivot on the second, and admitting of the performance of slight
lateral movements. It is formed by the opposing of the inferior surface of the os
suffraginis with the superior surface of the os coronæ. The articulating
surface of the os coronæ is supplemented by the addition behind of a thick
piece of fibro-cartilage (the glenoid) attached inferiorly to the posterior
edge of the upper articulatory surface of the os coronæ, and superiorly by
means of three fibrous slips on each side to the os suffraginis. The innermost of
these three slips becomes attached to about the middle of the lateral edge of the
suffraginis, and the remaining two, beneath the first, attach themselves to nearer
the lower end of that bone. The posterior surface of the complementary cartilage
forms a gliding surface for the passage of the perforans.

FIG. 6.—THE NAVICULAR BONE (VIEWED FROM BELOW).
1, Inferior surface (smooth for the passage of the flexor perforans); 2, anterior
edge of inferior surface; 3, posterior edge of inferior surface.

FIG. 7.—THE NAVICULAR BONE (VIEWED FROM ABOVE, THE BONE TILTED POSTERIORLY
TO SHOW ITS ANTERIOR BORDER).
1, Superior articulatory surface; 2, anterior border (grooved portion of); 3,
anterior border (articulatory portion of).

FIG. 8.—LIGAMENTS OF THE FIRST AND SECOND INTERPHALANGEAL ARTICULATIONS
(VIEWED FROM THE SIDE). (AFTER DOLLAR AND WHEATLEY.)
1, Outermost slip from the glenoidal fibro-cartilage; 2, lateral ligament of the
first interphalangeal articulation; 3, prolongations of the lateral ligament of the
first interphalangeal articulation attached to the end of the navicular bone to form
the postero-lateral ligament of the pedal joint; 4, end of the navicular bone; 5,
antero-lateral ligament of the pedal joint.

The Lateral Ligaments.—These are large and thick, an outer and an
inner, running obliquely from above downwards and backwards. Each is inserted
superiorly into the lateral tubercle of the lower end of the first phalanx, and
inferiorly to the side of the second phalanx, their most inferior fibres becoming
finally fixed to the extremities of the navicular bone, where they form the
postero-lateral ligaments of the pedal articulation. In front of the joint the
extensor pedis plays the part of an additional ligament.

The Synovial Membrane.—This is limited in front by the tendon of the
extensor pedis, on each side by the lateral ligaments of the joint, and behind by the
glenoid fibro-cartilage. At this point it is prolonged upwards as a pouch behind the
lower extremity of the first phalanx.

THE ARTICULATION OF THE SECOND PHALANX WITH THE THIRD, THE PEDAL, OR THE COFFIN
JOINT.—This also is an imperfect hinge-joint, permitting only of flexion and
extension, which movements are more restricted than in the previous articulation.
Three bones enter into its formation: the second phalanx, the third phalanx, and the
navicular bone. The lower articulatory surface is formed by the third phalanx and the
navicular bone combined. To effect this the navicular is closely and firmly attached
to the third phalanx by an interosseous ligament. The two bones, as one, are then
connected to the second phalanx by four lateral ligaments, an anterior and a
posterior on each side.

The Interosseous Ligament consists of extremely short fibres running from
the extensively grooved portion of the anterior surface of the navicular bone to
become attached to the os pedis immediately behind its articular surface.

The Antero-lateral Ligaments are attached by their superior extremities to
the lateral surfaces of the second phalanx, and by their inferior extremities into
the depressions on either side of the pyramidal process of the os pedis.

The Postero-lateral Ligaments.—As mentioned when describing the first
interphalangeal articulation, these are in reality continuations of the lateral
ligaments of that joint. Running obliquely downwards and backwards from their point
of attachment to the first phalanx they curve round the lower part of the side of the
second phalanx and end on the extremities and posterior surface of the navicular
bone. Having reached that position, they send short attachments to the retrossal
process of the os pedis and to the inner face of the lateral cartilage.

FIG. 9.—LIGAMENTS OF THE FIRST AND SECOND INTERPHALANGEAL ARTICULATIONS
(VIEWED FROM BEHIND). (AFTER DOLLAR AND WHEATLEY.) 1, Suspensory ligament; 2,
innermost slip from complementary cartilage of pastern joint; 3, middle slip from
complementary cartilage of pastern joint; 4, outermost slip from complementary
cartilage of pastern joint; 5, glenoid or complementary cartilage of pastern joint;
6, postero-lateral ligaments of the pedal joint; 7, the navicular bone; 8,
interosseous ligaments of the pedal joint; 9, semilunar crest of os pedis; 10,
plantar surface of os pedis.

Synovial Membrane.—This extends below the facets uniting the
navicular to the pedal bone, and offers for consideration two sacs. A large one
posteriorly running up behind the second phalanx to nearly adjoin the sesamoidean
bursæ, and a small one, a prolongation of the synovial membrane between the
antero-lateral and postero-lateral ligaments of the same side. This latter is often
distended, and on account of its close proximity to the seat of operation, is liable
to be accidentally opened in excision of the lateral cartilage for quittor.

C. THE TENDONS

In order to convey an intelligent understanding of the tendons it will be wise to
briefly describe the course of their parent muscles from their commencement.

THE EXTENSOR PEDIS.—The extensor pedis arises from the lower extremity of
the humerus in two distinct portions of unequal size, a muscular and a tendinous.
These are succeeded by two tendons passing in common through a vertical groove at the
lower end of the radius. Lower in the limb these tendons separate, the outer and
smaller joining the tendon of the extensor suffraginis, and the inner and main tendon
continuing its course downwards. With the exception of the navicular, it is attached
to all the bones of the foot, and is covered internally by the capsular ligaments of
the joints over which it passes, those with which we are concerned being the pastern
joint and the pedal joint. Before its attachment to the os pedis it receives on each
side of the middle of the first phalanx reinforcement in the shape of a strong band
descending obliquely over the fetlock from the suspensory ligament. Widening out in
fanlike fashion, it is inserted into the pyramidal process of the os pedis.

Action.—The action of this muscle is to extend the third phalanx on
the second, the second on the first, and the first on the metacarpus. It also assists
in the extension of the foot on the forearm.

FIG. 10.—THE FLEXOR TENDONS AND EXTENSOR PEDIS. (AFTER HAÜBNER.) 1,
Tendon of flexor perforans; 2, its supporting check-band from the posterior ligament
of the carpus; 3, tendon of the flexor perforatus; 4, ring and sheath of the flexor
perforatus; 5, widening out of the flexor perforatus to form the plantar aponeurosis;
6, suspensory ligament; 7, reinforcing band from the suspensory ligament to the
extensor pedis; 8, the extensor pedis.

THE FLEXOR PEDIS PERFORATUS, OR THE SUPERFICIAL FLEXOR OF THE PHALANGES.—In
common with the perforans, this muscle arises from the inner condyloid ridge of the
humerus. It is reinforced at the lower end of the radius by the superior carpal
ligament, passes through the carpal and metacarpo-phalangeal sheaths, and, arriving
behind the fetlock, forms a ring for the passage of the flexor perforans. Its
termination is bifid, and it is inserted on either side to the lateral surface of the
second phalanx.

FIG. 11.—THE FLEXOR PERFORANS AND FLEXOR PERFORATUS TENDONS. The
metacarpo-phalangeal sheath and the ring of the perforatus laid open posteriorly, and
the cut edges reflected to show the passage of the perforans. 1, Reflected cut edges
of the perforatus ring and the metacarpo-phalangeal sheath; 2, the perforans tendon;
3, point of insertion of the perforans tendon into the semilunar crest of the os
pedis (this widened and thickened extremity of the perforans is known as the plantar
aponeurosis).

FIG. 12.—THE FLEXOR PERFORATUS AND FLEXOR PERFORANS TENDONS. The
metacarpo-phalangeal sheath and the ring of the perforatus laid open posteriorly, and
the cut edges reflected; the flexor perforans cut through at about the region of the
sesamoids, and its inferior portion deflected. 1, Superior end of severed perforans
tendon; 2, inferior end of severed perforans tendon; 3, insertion of flexor perforans
into semilunar crest of os pedis; 4, the cut and reflected edges of the
metacarpo-phalangeal sheath and perforatus ring; 5, the bifid insertion of the flexor
perforatus into the lateral surfaces of the os corona; 6, the capsular ligament of
the pedal joint; 7, the navicular bone; 8, the posterior surface and glenoid
fibro-cartilage of the os coronæ.

Action.—This muscle flexes the second phalanx on the first, the first
on the metacarpus, and the entire foot on the forearm. Mechanically, it acts as a
stay when the animal is standing by maintaining the metacarpo-phalangeal angle.

FIG. 13.—MEDIAN SECTION OF FOOT. A, Os suffraginis; B, os
coronæ; C, os pedis; D, navicular bone; E, tendon of the
extensor pedis; F, insertion of the extensor pedis into the pyramidal process
of the os pedis; G, the tendon of the flexor perforatus; H, insertion
of perforatus into the os coronæ; I, tendon of the flexor perforans;
J, its passing attachment to the os coronæ; K, its final
insertion into the semilunar crest of os pedis; a, section of coronary
cushion; b, section of plantar cushion; c, semilunar sinus of os
pedis.

THE FLEXOR PEDIS PERFORANS, OR THE DEEP FLEXOR OF THE PHALANGES.—This muscle
consists of three easily-divided portions: an ulnar, a humeral, and a radial, and has
for points of origin the olecranon process of the ulna, the inner condyloid ridge of
the humerus, and the posterior surface of the radius. These portions are continued by
a common tendon which enters the carpal sheath with the tendon of the perforatus, and
continues with it through the synovial sheath of the metacarpo-phalangeal region.
Like the last-named tendon, it receives a supporting check-band, in this case from
the posterior ligament of the carpus. Passing down between the suspensory ligament in
front, and the perforatus tendon behind, it glides over the sesamoid pulley and
passes through the ring formed by the perforatus. Continuing its course, it passes
between the bifurcating portions of the extremity of the perforatus, glides over the
smooth posterior surface of the supplementary glenoid cartilage of the articulation
of the first and second phalanges, plays over the inferior surface of the navicular
bone, and finally becomes inserted into the semilunar crest of the os pedis. On
reaching the posterior border of the navicular bone it widens out to form the plantar
aponeurosis.

In connection with the lower portion of this tendon must be noticed the Navicular
Sheath. This is a synovial sheath lining the deep face of the tendon, and reflected
on to the navicular bone and the interosseous ligament of the pedal joint. This will
be of particular interest when we come to deal with cases of pricked foot from picked
up nails. Above, it is in connection with the synovial membrane of the pedal
articulation and that of the metacarpo-phalangeal sheath.

Action.—The action of the perforans is to flex the third on the
second, and the second on the first phalanx. The latter it flexes in turn on the
metacarpus. It also assists in the flexion of the entire foot on the forearm, and in
supporting the angle of the metacarpo-phalangeal articulation when the animal is
standing.

D. THE ARTERIES.

So far as the arteries supplying the foot are concerned, we shall be interested in
following up the distribution of the two digitals, which are the terminal branches of
the Large Metacarpal.

THE LARGE METACARPAL, OR COLLATERAL ARTERY OF THE CANNON.—This, the larger
terminal branch of the posterior radial artery, needs brief mention, for the reason
that we shall be afterwards concerned with it in the operation of neurectomy. Its
point of origin is the inside of the inferior extremity of the radius. Descending in
company with the flexor tendons, and passing behind the carpus and beneath the carpal
sheath, it continues its descent, in company with the internal plantar nerve and the
internal metacarpal vein, on the inner side of the flexor tendons until just above
the fetlock. At this point it bifurcates into the digital arteries.

From the carpus downwards the large metacarpal artery, the internal metacarpal
vein, and the internal plantar nerve are in close relation with each other. The vein
holds the anterior position. The artery is between the two, and has the nerve in
close contact with it behind.

THE DIGITAL ARTERIES, OR COLLATERAL ARTERIES OF THE DIGIT.—These are of
large volume, and carry the blood to the keratogenous apparatus of the foot. They
separate from each other at an acute angle, and pass over the side of the fetlock,
one to the inside, the other to the outside, to reach the internal face of the
basilar process of the os pedis, where they bifurcate to form the Plantar and
Preplantar arteries. In the whole of their course the digital arteries follow
the flexor tendons, and are related in front to the digital vein, and behind to the
posterior branch of the plantar nerve. This is the nerve implicated in the lower
operation of neurectomy, and its relation to adjoining structures will be detailed
under Section F. of this chapter. During its course the digital artery gives off
branches in the following positions:

1. At the Fetlock numerous branches to the metacarpo-phalangeal
articulation, the sesamoid sheath, and the tendons.

2. At the Upper Extremity of the First Phalanx branches for the supply of
the surrounding tissues, and for the tissues of the ergot.

3. Towards the Middle of the Third Phalanx, the Perpendicular artery
of Percival. This arises at a right angle from the main vessel, and immediately
divides into two series of ramifications—an ascending and a descending. The
ramifications of these series freely anastomose with corresponding vessels of the
opposite side.

4. At the Superior Border of the Lateral Cartilage, the Artery of the
Plantar Cushion. This is directed obliquely downwards and backwards, under cover
of the cartilage, and is distributed to the middle portion of the complementary
apparatus of the os pedis, as well as to the villous tissue and the coronet. A branch
of it is turned forwards to join with the coronary circle in forming the
circumflex artery of the coronet.

FIG. 14.—THE ARTERIES OF THE FOOT. The digital; 2, the
perpendicular—(a) its ascending branch, (b) its descending
branch; 3, circumflex artery of coronary cushion; 4, the preplantar (ungual)
artery—this is seen issuing from the preplantar foramen, and distributing
numerous ascending (c) and descending (d) branches (the latter concur
in forming the circumflex artery of the toe); 5, the circumflex artery of the toe; 6,
at the point marked (*) the terminal branch of the digital—namely, the plantar
ungual—is hidden behind the lateral cartilage; 7, the lateral cartilage.

5. Under the Lateral Cartilage two transverse branches, an anterior and a
posterior, to form the Coronary Circle. The numerous ramifications of these
branches anastomose both anteriorly and posteriorly with their corresponding branches
of the artery of the opposite side. This circle closely embraces the os coronæ.
Among the larger branches given off from its anterior portion are two descending, one
on each side of the extensor pedis, to assist in the formation of the Circumflex
Artery of the Coronary Cushion. The formation of this last-named artery is
completed posteriorly by the before-mentioned branch from the artery of the plantar
cushion.

THE PREPLANTAR (UNGUAL[A]) ARTERY.—This, the smaller of the two terminal
branches of the digital, is situated inside the basilar process of the os pedis. It
turns round this to gain the fissure between the basilar and retrossal processes, and
becomes lodged in the preplantar fissure. Here it terminates in several divisions
which bury themselves in the os pedis. Before leaving the inner aspect of the pedal
wing it supplies a deep branch to the heel and the villous tissue. Gaining the outer
aspect of the wing, it distributes a further backward branch, which passes behind the
circumflex artery of the pedal bone, and, during its passage in the preplantar
fissure, gives off ascending and descending branches, which ramify in the laminal
tissue.

THE PLANTAR (UNGUAL[A]) ARTERY.—This, the larger of the two terminals of the
digital, may be looked upon as a continuation of the main vessel. Running along the
plantar groove, it gains the plantar foramen. Here it enters the interior of the bone
(the semilunar sinus) and anastomoses with the corresponding artery of the opposite
side. The circle of vessels so formed is called the Plantar Arch or the
Semilunar Anastomosis.

[Footnote A: The epithet ‘ungual’ is added by Chauveau to distinguish these
arteries from the properly so-called plantar arteries—the terminal divisions of
the posterior tibial artery.]

From the semilunar anastomosis radiate two main groups of arterial branches, an
ascending group and a descending one. The ascending branches penetrate the
substance of the os pedis, and emerge by the numerous foraminæ on its laminal
surface. The descending branches, larger in size, also penetrate the substance
of the pedal bone, and emerge in turn from the foraminæ cribbling its outer
surface—in this case the set of larger foraminæ opening on its inferior
edge. Having gained exit from the bone, their frequent anastomosis, right and left,
with their fellows forms a large vessel following the contour of the inferior edge of
the os pedis. This constitutes the Circumflex Artery of the Toe.

E. THE VEINS.

These commence at the foot with a series of plexuses, which may be described as
forming (1) AN INTERNAL OR INTRA-OSSEOUS VENOUS SYSTEM, and (2) AN EXTERNAL OR
EXTRA-OSSEOUS VENOUS SYSTEM.

1. THE INTRA-OSSEOUS VENOUS SYSTEM.—This is a venous system within the
structure of, and occupying the semilunar sinus of the os pedis. It follows in every
respect the arrangement of the arteries as before described in the same region.
Efferent vessels emerge from the plantar foraminæ, follow the plantar fissures,
and ascend within the basilar processes of the os pedis. Here they lie under shelter
of the lateral cartilages, and assist in the formation of the deep layer of the
coronary plexus of the extra-osseous system.

2. THE EXTRA-OSSEOUS VENOUS SYSTEM.—This may be regarded as a close-meshed
network enveloping the whole of the foot. Although a continuous system, it is best
described by recognising in it three distinct parts:

(a) The Solar Plexus.
(b) The Podophyllous Plexus.
(c) The Coronary Plexus.

(a) The Solar Plexus.—The veins of this plexus discharge themselves
in two directions: (1) By a central canal or canals running along the bottom
of the lateral lacunæ of the plantar cushion to gain the deep layer of the
coronary plexus. (2) By the Circumflex or Peripheral Vein of the Toe, a canal
formed by ramifications from the solar and the podophyllous plexuses, and following
the direction of the artery of the same name. The circumflex vein terminates by
forwarding branches to concur in the formation of the superficial coronary
plexus.

(b) The Podophyllous or Laminal Plexus.—The podophyllous veins
anastomose below with the circumflex vein of the solar plexus, and above with the
veins of the coronary plexus.

(c) The Coronary Plexus.—This proceeds from the podophyllous, the
intra-osseous, and the solar networks, and consists of a central and two
lateral parts.

The central portion lies between the lateral cartilages and immediately
under the coronary cushion. The lateral portions are ramifications on both
surfaces of the lateral cartilages. The ramifications on the lateral cartilages may
be again distinguished as superficial and deep. The superficial layer
is distributed over the external face of the cartilage, forming thereon a dense
network, and finally converges towards the superior limit of the plexus to form ten
or twelve principal branches, which again unite to form two large vessels. These
vessels, by their final fusion at the lower end of the first phalanx, constitute the
digital vein. The deep layer is formed, as before described, by ascending branches
from the posterior parts of the podophyllous and solar plexuses, and by branches from
the intra-osseous system of the pedal bone. The veins of this deep layer finally
drain into the two vessels proceeding from the superficial layer, which go to the
formation of the digital vein.

THE DIGITAL VEINS—These arise from the network formed on the surfaces of the
lateral cartilages, and ascend in front of the digital arteries to unite above the
fetlock, where they form an arch between the deep flexor and the suspensory ligament.
From this arch (named the Sesamoidean) proceed the Metacarpal Veins.

THE METACARPAL VEINS.—Three in number, they are distinguished as an
Internal and an External Metacarpal, and a Deep or
Interosseous Metacarpal. As we shall be concerned with these in the higher
operation of neurectomy, we may give them brief mention.

THE INTERNAL METACARPAL VEIN, the largest of the three, has relations with the
internal metacarpal artery and the internal plantar nerve. These relations were
shortly discussed under the section devoted to the arteries, to which the reader may
refer.

THE EXTERNAL METACARPAL VEIN.—This ascends on the external side of the
flexor tendons in company with the external plantar nerve.

The Interosseous Vein.—This is an irregular vessel running up between
the suspensory ligament and the posterior face of the large metacarpal bone.

F. THE NERVES.

THE PLANTAR NERVES.—These are two in number, and are distinguished as
Internal and External.

THE INTERNAL PLANTAR NERVE lies behind and in close contact with the great
metacarpal artery during that vessel’s course down the region of the cannon. A point
of interest is that it gives off at about the middle of the cannon a branch which
bends obliquely downwards and behind the flexor tendons to join its fellow of the
opposite side—namely, the external plantar. This it joins an inch or more above
the bottom of the splint bone. Measured in a straight line, this is about 2-1/2
inches below its point of origin. Near the fetlock, at the level of the sesamoids,
the internal plantar nerve ends in several digital branches.

THE EXTERNAL PLANTAR NERVE.—This holds a position to the outside of the
metacarpal region, analogous to that of the internal plantar nerve on the inside of
the limb, running down on the external edge of the flexor tendons. Unlike the
internal nerve, it is accompanied by a single vessel only, the external metacarpal
vein, behind which it lies. At the level of the sesamoid bones it divides, as does
the internal nerve, into three main branches—the digital nerves.

FIG. 15.—THE VEINS AND NERVES OF THE FOOT. 1, The digital vein; 2, its main
tributaries, draining the podophyllous plexus, and concurring to form the digital; 3.
the digital artery (the main trunk only of this is shown, in order to show its
relationship with the vein and nerve); 4, the plantar nerve, with its three
branches—(a) the anterior digital, (b) the middle digital,
(c) the posterior digital; 5, the podophyllous plexus; 6, superficial portion
of the coronary plexus; 7, the peripheral or circumflex vein of the toe.

THE DIGITAL NERVES.—These are distinguished as Anterior, Middle, and
Posterior.

The Anterior Branch descends in front of the vein, distributing cutaneous
branches to the front of the digit, and terminating in the coronary cushion.

The Middle Branch descends between the artery and the vein, and freely
anastomoses with the two other branches. It terminates in the coronary cushion and
the sensitive laminæ.

The Posterior Branch.—This is the largest of the three, and may be
regarded as the direct continuation of the plantar. At the fetlock it is placed
immediately above the digital artery, but afterwards takes up a position directly
behind that vessel. Together with the digital artery it descends to near the basilar
process of the os pedis. Here it passes with the plantar artery into the interior of
the os pedis, and continues its main branch, with the preplantar artery, in the
fissure of the same name, to finally furnish supply to the os pedis and the sensitive
laminæ. It is this nerve which is divided in the low operation of
neurectomy.

Beyond the fact of this branch descending, in the region of the pastern, 1 inch
behind the digital artery, a further point of interest presents itself to the
surgeon, and one to which attention must be paid. This is the presence in close
proximity to the nerve of the Ligament of the Pad (Percival), or the Ligament of the
Ergot (McFadyean). This is a subcutaneous glistening cord originating in the ergot of
the fetlock, passing in an oblique direction downwards and forwards, and crossing
over on its way both the digital artery and the posterior branch of the digital
nerve.

In the foregoing description of the anatomy, we have taken the fore-limb as our
guide. In the hind-limb, where they reach the foot, the counterparts of the tendons,
arteries, veins, and nerves differ in no great essential from their fellows in the
fore. They will therefore need no special mention.

G. THE COMPLEMENTARY APPARATUS OF THE OS PEDIS.

This consists of two lateral pieces, the LATERAL CARTILAGES or
Fibro-cartilages of the pedal bone, united behind and below by the Plantar
Cushion.

1. THE LATERAL CARTILAGES.—Each is a flattened plate of cartilage,
possessing two faces and four borders separated by four angles.

The external face is convex, covered by a plexus of veins, and slightly overhangs
the pedal bone. The internal face is concave, and covers in front the pedal
articulation and the synovial sac, already mentioned as protruding between the
antero- and postero-lateral ligaments of that joint. We have already remarked that
this is a point of interest to be remembered in connection with the operation for
quittor. Below and behind, the internal face of the cartilage is united to the
plantar cushion.

FIG. 16.—EXTERNAL FACE OF THE OUTER LATERAL CARTILAGE. 1, External face of
cartilage—(a) its upper border, (b) its posterior border,
(c) its anterior border, (d) its inferior border; 2, the os pedis; 3,
wing of os pedis.

The upper border, sometimes convex, sometimes straight, is thin and bevelled, and
may easily be felt in the living animal. It is this border that the digital vessels
cross to gain the foot, and the border is often broke by a deep notch to accommodate
them. The inferior border is attached in front to the basilar and retrossal
processes, behind which it blends with the plantar cushion. The posterior border is
oblique from before to behind, and above to below, and joins the preceding two. The
anterior border is oblique in the same direction, and is intimately attached to the
antero-lateral ligament of the pedal articulation. The cartilages of the fore-feet
are thicker and more extensive than those of the hind.

2. THE PLANTAR CUSHION on FIBRO-FATTY FROG.—Composed of a fibrous meshwork,
in the interstices of which are lodged fine elastic and connective fibres and fat
cells, this wedge-shaped body occupies the space between the two lateral cartilages,
the extremity of the perforans tendon, and the horny frog. It offers for
consideration an antero-superior and an infero-posterior face, a base, an apex, and
two borders.

The antero-superior face is in contact with the terminal expansion of the
perforans tendon. The infero-posterior face is covered by the keratogenous membrane,
and follows closely the shape of the horny frog, on whose inner surface it is
moulded. It presents, therefore, at its centre a single conical prolongation, the
Pyramidal Body, which is continued behind, as is the horny frog, in the shape
of two lateral ridges divided by a median cleft. The base of the cushion lies
behind, and consists of two lateral masses, the Bulbs of the Plantar Cushion.
In front these are continuous with the ridges of the pyramidal body, while behind
they become confounded with the lateral cartilages and the coronary cushion. The
apex is fixed into the plantar surface of the os pedis, in front of its
semilunar ridge. The borders, right and left, are wider behind than before,
and are in relation with the inner faces of the lateral cartilages.

H. THE KERATOGENOUS MEMBRANE.

THE KERATOGENOUS, OR HORN-PRODUCING MEMBRANE, is in reality an extension of the
dermis of the digit. It covers the extremity of the digit as a sock covers the foot,
spreading over the insertion of the extensor pedis, the lower half of the external
face of the lateral cartilages, the bulbs of the plantar cushion, the pyramidal body,
the anterior portion of the plantar surface of the os pedis, and over the anterior
face of the same bone. In turn, as the human foot with its sock is covered by the
boot, this is encased by the hoof, the formation of which we shall study later.

To expose the membrane for study the hoof must be removed. This may be done in two
ways. By roasting in a fire, and afterwards dragging off the horny structures with a
pair of pincers, a knife having first been passed round the superior edge of the
horny box. Or by maceration in water for several days, when the hoof will become
loosened by the process of decomposition, and may be easily removed by the hands. The
latter method is less likely to injure the sensitive structures, and will expose them
with a fresh appearance for observation.

For purposes of description the keratogenous membrane is divided into three
regions:

1. The Coronary Cushion.
2. The Velvety Tissue.
3. The Podophyllous Tissue, or the Sensitive Laminæ.

1. THE CORONARY CUSHION. In the foot stripped of the hoof the coronary cushion is
seen as a rounded structure overhanging the sensitive laminæ after the manner
of a cornice. It extends from the inner to the outer bulbs of the plantar cushion,
and is bounded above by the perioplic ring, and below by the laminæ.

When in situ it is accommodated by the Cutigeral Groove, a cavity
produced by the bevelling out of the superior portion of the inner face of the wall
of the hoof. Its superior surface is covered by numerous elongated papillæ, set
so closely as to give the appearance of the ‘pile’ of velvet. This is observed to the
best advantage with the foot immersed in water.

The Superior Border of the cushion is bounded by the Perioplic Ring,
the cells of which have as their function the secreting of the Periople, a
layer of thin horn to be noted afterwards as covering the external face of the wall.
From the perioplic ring the cushion is separated by a narrow and shallow, though
well-marked, groove.

The inferior border is bounded by the sensitive laminæ.

FIG. 17.—THE KERATOGENOUS MEMBRANE (VIEWED FROM THE SIDE). (THE HOOF REMOVED
BY MACERATION.) 1. The sensitive laminæ, or podophyllous tissue; 2, the
coronary cushion; 3, the perioplic ring; 4, portion of plantar cushion; 5, groove
separating perioplic ring from coronary cushion; 6. the sensitive sole.

The upper portions of the laminæ, those in contact with the cushion, are
pale in contrast with the portions immediately below, and thus there is given the
appearance of a white zone adjoining the inferior border of the cushion.

Widest at its centre, the cushion narrows towards its extremities, which, arriving
at the bulbs of the plantar cushion, bend downwards into the lateral lacunæ of
the pyramidal body, where they merge into the velvety tissue of the sole and
frog.

The papillæ of the coronary cushion secrete the horn tubules forming the
wall, and the papillæ of the perioplic ring secrete the varnish-like veneer of
thin horn covering the outside surface of the hoof.

FIG. 18.—THE KERATOGENOUS MEMBRANE (VIEWED FROM BELOW). (THE HOOF REMOVED BY
MACERATION.) 1, The sensitive sole; 2, the sensitive frog[A]—(a) its median
lacuna, (6) its lateral lacuna; 3. V-shaped depression accommodating the toe-stay; 4,
the sensitive laminæ which interleave with the horny laminæ of the
bar.

[Footnote A: The sensitive frog thinly invests the plantar cushion or fibre-fatty
frog, the outline of which is here indicated.]

2. THE VELVETY TISSUE.—This is the portion of the keratogenous membrane
covering the plantar surface of the os pedis and the plantar cushion. To the
irregularities of the latter body—its bulbs, pyramidal body, and its
lacunæ—it is closely adapted. Its surface may, therefore, be divided into
(a) The Sensitive Frog, and (b) The Sensitive Sole.

(a) The Sensitive Frog is that part of the velvety tissue moulded on the
lower surface of the plantar cushion. The shape of the plantar cushion has already
been described as identical with that of the horny frog. It only remains to state
that, like the coronary cushion, the surface of the sensitive frog is closely studded
with papillæ. The cells clothing the papillæ are instrumental in forming
the horny frog.

(b) The Sensitive Sole.—As its name indicates, this is the portion of
the keratogenous membrane that covers the plantar surface of the os pedis. It also is
clothed with papillæ, which again give rise to the formation of that part of
the horny box to which they are adapted—namely, the sole.

3. THE PODOPHYLLOUS TISSUE, OR SENSITIVE LAMINÆ.—This portion of the
keratogenous membrane is spread over the anterior face and sides of the os pedis,
limited above by the coronary cushion, and below by the inferior edge of the bone. It
presents the appearance of fine longitudinal streaks, which, when closely examined
with a needle, are found to consist of numerous fine leaves. These extend downwards
from the lower border of the coronary cushion to the inferior margin of the os pedis.
At this point each terminates in several large villous prolongations, which extend
into the horny tubes at the circumference of the sole. At the point of the toe this
membrane sometimes shows a V-shaped depression, into which fits a inverted V-shaped
prominence on the inner surface of the wall at this point.

The sensitive laminæ increase in width from above to below. Their free
margin is finely denticulated, while their sides are traversed from top to bottom by
several folds (about sixty), which, examined microscopically, are seen to consist of
secondary leaves, or laminellæ.

Examined on the foot, deprived of its horny covering, the sensitive laminæ
are, the majority of them, in close contact with each other. In the normal state this
is not so. The interstices between the leaves are then occupied by the horny leaves,
to be afterwards described as existing on the inner surface of the wall.

Reaching and rounding the heels, the sensitive laminæ extend forward for a
short distance, where they interleave with the horny laminæ of the bars.

Much discussion has centred round the point as to whether or no the cells of the
sensitive laminæ take any share in the formation of the horn of the wall. This
will be alluded to in a future chapter.

I. THE HOOF.

Removed from the foot by maceration a well-shaped hoof is cylindro-conical in
form, and appears to the ordinary observer to consist of a box or case cast in one
single piece of horn. Prolonged maceration, however, will show that the apparently
single piece is divisible into three. These are known as (1) THE WALL, (2) THE SOLE,
and (3) THE FROG. In addition to these, we have also an appendage or circular
continuation of the frog named (4) THE PERIOPLE, or CORONARY FROG BAND. These various
divisions we will study separately.

1. THE WALL is that portion of the hoof seen in front and laterally when the
horse’s foot is on the ground. Posteriorly, instead of being continued round the
heels to complete the circle, its extremities become suddenly inflected downwards,
forwards, and inwards. These inflections can only be seen with the foot lifted from
the floor, and form the so-called Bars. It will be noticed, too, with the foot
lifted, that the wall projects beyond the level of the other structures of the
plantar surface, taking upon itself the bearing of the greatest part of the animal’s
weight.

The horn of the wall, viewed immediately from the front, is known as the
Toe, which again is distinguished as Outside Toe or Inside Toe,
according as the horn to its inner or outer aspect is indicated. The remainder of the
external face of the wall, that running back to the heels, is designated the
Quarters.

In the middle region of the toe, the wall following the angle of the bones is
greatly oblique. This obliquity decreases as the quarters are reached, until on
reaching the heels the wall is nearly upright.

FIG. 19.—THE WALL OF THE HOOF. 1, The toe; 2, inner toe; 3, outside toe; 4,
the quarter; 5, entigeral groove; 6, horny laminæ.

For observation the wall offers two faces, two borders, and two extremities.

The External Face is convex from side to side, but straight from the upper
to the lower border. Examined closely, it is seen to be made up of closely-arranged
parallel fibres running in a straight line from the upper to the lower border, and
giving the surface of the foot a finely striated appearance. In addition to these
lines, which are really the horn tubules, the external face is marked by a series of
rings which run horizontally from heel to heel. These are due to varying influences
of food, climate, and slight or severe disease. This will be noted again in a later
page. In a young and healthy horse the whole of the external face of the wall is
smooth and shining. This appearance is due to a thin layer of horn, secreted
independently of the wall proper, termed the periople.

FIG. 20.—INTERNAL FEATURES OF THE WALL, FROG, AND SOLE (MESIAN SECTION OF
HOOF). 1, Horny laminæ covering internal face of wall; 2, superior border of
wall; 3, junction of wall with horny sole; 4, the cutigeral groove; 5, the horny
sole; 6, the horny frog (that portion of it known as the ‘frog-stay’); 7, inverted
V-shaped ridge on wall and sole (known as the ‘toe-stay’); 8, anterior face of wall;
9, inferior border of wall.

The Internal Face of the wall, that adapted to the sensitive laminæ,
is closely covered over its entire surface with white parallel leaves
(Keraphyllæ, or horn leaves, to distinguish them from the
Podophyllæ, or sensitive leaves). These keraphyllæ dovetail
intimately with the sensitive laminæ, covering the os pedis. Running along the
superior portion of the inner face is the Cutigeral Groove. This cavity has
been mentioned before as accommodating the coronary cushion, whose shape and general
contour it closely follows, being widest and deepest in front, and gradually
decreasing as it proceeds backwards. It is hollowed out at the expense of the wall,
and shows on its surface numberless minute openings which receive the papillæ
of the coronary cushion.

At the bottom of the internal face, at the point where the toe joins the sole,
will be noted the before-mentioned inverted V-shaped prominence. Its position will be
clearly understood when we say that it gives the appearance of having been forced
there by the pressure of the toe-clip of the shoe. This will be noted again when
dealing with the sole.

The Inferior Border of the wall offers little to note. It is that portion
in contact with the ground, and subject to wear. A point of interest is its union
with the sole. This will be noticed in a foot which has just been pared as a narrow
white or faint yellow line on the inner or concave face of the wall at its lower
portion. It marks the point where the horny leaves of the wall terminate and become
locked with corresponding leaves of the circumference of the sole.

The Superior Border follows closely the line marked by the perioplic ring
and the groove separating the latter from the coronary cushion.

The Extremities of the wall are formed by the abruptly reflected portions
of the wall at the heels. Termed by some the ‘Inflexural Nodes,’ they are better
known to us as the ‘Points of the Heels.’

2. THE SOLE.—The sole is a thick plate of horn which, in conjunction with
the bars and the frog, forms the floor of the foot. In shape it is irregularly
crescentic, its posterior portion, that between the horns of the crescent, being
deeply indented in a V-shaped manner to receive the frog. Its upper surface is
convex, its lower concave. It may be recognised as possessing two faces and two
borders.

The Superior or Internal Face is adapted to the sole of the os pedis. Its
highest point, therefore, is at the point of its V-shaped indentation. From this
point it slopes in every direction downwards and outwards until near the
circumference. Here it curves up to form a kind of a groove in which is lodged the
inferior edge of the os pedis. In the centre of its anterior portion—that is to
say, at the toe—will be seen a small inverted V-shaped ridge, which is a direct
continuation of the same shaped prominence before mentioned on the internal face of
the wall. This Fleming has termed the toe-stay, from a notion that it serves to
maintain the position of the os pedis. The whole of the superior face of the sole is
covered with numerous fine punctures which receive the papillæ of the sensitive
sole.

The Inferior Face is more or less concave according to circumstances, its
deepest part being at the point of the frog. Sloping from this point to its
circumference, it becomes suddenly flat just before joining the wall. Its horn in
appearance is flaky.

FIG. 21.—INFERIOR ASPECT OF HOOF. a The inferior face of horny sole;
b, inferior border of the wall; c, body or cushion of the frog;
d, median lacuna of the frog; e, lateral lacuna of the frog; f,
the bar; g, the quarter; h, the point of the frog; i the
heel.

The External Border or Circumference is intimately dovetailed with the
horny laminæ of the wall. At its circumference the sole, if unpared, is
ordinarily as thick as the wall. This thickness is maintained for a short distance
towards its centre, after which it becomes gradually more thin.

The Internal Border has the shape of an elongated V with the apex pointing
forwards. It is much thinner than the external border, and, like it, is dovetailed
into the horny laminæ of the inflections of the wall—namely, the bars. In
front of the termination of the bars it is dovetailed into the sides and point of the
frog. Where unworn by contact with the ground, the horn of the sole is shed by a
process of exfoliation.

3. THE FROG.—Triangular or pyramidal in shape, the frog bears a close
resemblance to the form of the plantar cushion, upon the lower surface of which body
it is moulded. It offers for consideration two faces, two sides, a base, and a point
or summit.

FIG. 22.—HOOF WITH THE SENSITIVE STRUCTURES REMOVED. 1, Superior face of
horny frog; 2, the frog-stay; 3, the lateral ridges of the frog’s superior surface;
4, the horny laminæ at the inflections of the wall.

The Superior Face is an exact cast of the lower surface of the plantar
cushion. It shows in the centre, therefore, a triangular depression, with the base of
the triangle directed backwards. Posteriorly, the depression is continued as two
lateral channels divided by a median ridge. The median ridge widens out as it passes
backwards, forming the larger part of the posterior portion of the frog. This median
ridge fits into the cleft of the plantar cushion. It serves to prevent displacement
of the sensitive from the horny frog, and has been rather aptly termed the
‘Frog-stay.’

The Inferior Surface is an exact reverse of the superior. The triangular
depression of the superior surface is represented in the inferior surface by a
triangular projection, and the ridge-like frog-stay of the upper surface is
represented below by a median cleft, the Median Lacuna of the frog. The
triangular projection in front of the median lacuna is the body or cushion of the
frog. It is continued backwards as two ridge-like branches, which, at the points of
the heels, form acute angles with the bars. On the outer side of each lateral ridge
is a fissure. These are known as the Lateral Lacunæ.

The Sides of the frog are flat and slightly oblique. They are closely
united to the bars and to the triangular indentation in the posterior border of the
sole.

The Base of the frog is formed by the extremities of its branches, which,
becoming wider and more convex as they pass backwards, form two rounded, flexible,
and elastic masses separated from each other by the median lacuna. These constitute
the ‘glomes’ of the frog. They are continuous with the periople.

The Point of the Frog is situated, wedge-like, within the triangular notch
in the posterior border of the sole.

4. THE PERIOPLE, OR CORONARY FROG BAND.—This is a continuation of the
substance of the frog around the extreme upper surface of the hoof. It is widest at
the heels over the bulbs or glomes of the frog, and gradually narrows as it reaches
the front of the hoof. It is, in reality, a thin pellicle of semi-transparent horn
secreted by the cells of the perioplic ring. When left untouched by the farrier’s
rasp it serves the purpose, by acting as a natural varnish, of protecting the horn of
the wall from the effects of undue heat or moisture.

CHAPTER III

GENERAL PHYSIOLOGICAL AND ANATOMICAL
OBSERVATIONS

The matter embraced by the heading of this chapter will offer for discussion many
subjects of great interest to the veterinary surgeon. Around some of them debate has
for many years waxed more than keen. Of the points in dispute, some of them may be
regarded as satisfactorily settled, while others offer still further room for
investigation.

In this volume we can only hope to deal with them in brief, and must select such
as appear to have the greatest bearing on the veterinarian’s everyday practice.

Always prolific of heated discussion has been one question: ‘Are the horny
laminæ secreted by the sensitive?’ To answer this satisfactorily, it will be
best to give a short account of the mode of production of the hoof in general.

A. DEVELOPMENT OF THE HOOF.

Starting with the statement that it is epidermal in origin, we will first consider
the structure of the skin, and follow that with a brief description of the structure
and mode of growth of the human nail, a short study of which will greatly assist us
when we come to investigate the manner of growth of the horse’s hoof.

THE SKIN is composed of two portions, the EPIDERMIS and the CORIUM.

THE EPIDERMIS is a stratified epithelium. The superficial layers of the cells
composing it are hard and horny, while the deeper layers are soft and protoplasmic.
These latter form the so-called Rete Mucosum of Malpighi.

FIG. 23.—VERTICAL SECTION OF EPIDERMIS (HUMAN). (AFTER RANVIER) A,
The horny layer of the epidermis; B, the rete mucosum; a, the columnar
pigment-containing cells of the rete; b, the polyhedral cells; c, the
stratum granulosum; d, the stratum lucidum; e, swollen horny cells;
f the stratum squamosum.

Commencing from below and proceeding upwards, we find that the lowermost cells of
the rete mucosum, those that are set immediately on the corium, are columnar in
shape. In animals that have a coloured skin these cells contain pigment granules.
Directly superposed to these we find cells which in shape are polyhedral. Above them,
and forming the most superficial layer of the rete mucosum, is a series of flattened,
granular-looking cells known as the stratum granulosum.

Immediately above the stratum granulosum the horny portion of the epidermis
commences. In the human skin this is formed of three distinct layers. Undermost a
layer of clear compressed cells, the stratum lucidum. Next above it a layer of
swollen cells, the nuclei of which are indistinguishable. Finally, a surface layer of
thin, horny scales, the stratum squamosum, which become detached and thrown
off in the form of scurf or dandruff. In the skin of the horse, except where it is
thickest, these layers are not clearly defined.

It is the Malpighian layer of the epidermis that is most active in cell division.
As they are formed the new cells push upwards those already there, and the latter in
their progress to the surface undergo a chemical change in which their protoplasm is
converted into horny material. This change, as we have already indicated, takes place
above the stratum granulosum.

In addition to its constant formation of cells to replace those cast off from the
surface, the active proliferation of the elements of the Malpighian layer is
responsible for the development of the various appendages of the skin, the hairs with
their sebaceous glands, the sweat glands, horny growths and the hoof, and, in the
human subject, the nail. These occur as thickenings and down-growths of the
epithelium into the corium.

The epidermis is devoid of bloodvessels, but is provided with fine nerve fibrils
which ramify between the cells of the rete mucosum.

THE CORIUM is composed of dense connective tissue, the superficial layer of which
bears minute papillæ. These project into the epidermis, which is moulded on
them. For the most part the papillæ contain looped capillary vessels, rendering
the superficial layer of the corium extremely vascular. Why this must be a moment’s
reflection will show. The epidermis, as we have already said, is devoid of
bloodvessels. It therefore depends entirely for its nourishment upon the indirect
supply it receives from the vessels of the corium. The need for extreme vascularity
of the corium is further explained when we call to mind the constant proliferation
and casting off of the cells of the epidermis, the growth of the hairs, the
production of the horn of the hoof, and the work performed by the numerous sweat and
other glands.

Others of the papillæ contain nerves, ending here in tactile corpuscles, or
continuing, as we have mentioned before, to ramify as fine fibrils in the rete
mucosum of the epidermis.

THE HAIRS are growths of the epidermis extending downwards into the deeper part of
the corium. Each is developed in a small pit, the Hair Follicle, from the
bottom of which it grows, the part lying within the follicle being known as the
Root. It is important to note their structure, as it will be seen later that
they bear an extremely close relation to the horn of the hoof.

Under a high power of the microscope, and in optical section, the central portion
of a hair is tube-like. In some cases the cavity of the tube is occupied by a dark
looking substance formed of angular cells, and known as the Medulla. The walls
of the tube, or the main substance of the hair, is made up of a pigmented, horny,
fibrous material. This fibrous structure is covered by a delicate layer of finely
imbricated scales, and is termed the Hair Cuticle.

The root of the hair, that portion within the follicle, has exactly the same
formation save at its extreme end. Here it becomes enlarged into a knob-like
formation composed of soft, growing cells, which knob-like formation fits over a
vascular papilla projecting up in the bottom of the follicle.

We have already stated that the hairs are down-growths of the epidermis. It
follows, therefore, that the hair follicles, really depressions or cul-de-sacs of the
skin itself, are lined by epithelial cells and connective tissue. So closely does the
epidermal portion of the follicle invest the hair root that it is often dragged out
with it, and is known as the Root Sheath. This is made up of an outer layer of
columnar cells (the outer root sheath) corresponding to the Malpighian layer
of the epidermis, and of an inner horny layer, next to the hair, corresponding to the
more superficial layer of the epidermis, and known as the inner root
sheath.

The hair grows from the bottom of the follicle by a multiplication of the cells
covering the papilla upon which its root is moulded. When a hair is cast off a new
one is produced from the cells covering the papilla, or, in case of the death or
degeneration of the original papilla, the new hair is produced from a second papilla
formed in place of the first at the bottom of the follicle.

FIG. 24.—SECTION OF SKIN WITH HAIR FOLLICLE AND HAIR. a, The hair
follicle; b, the hair root; c, the medulla; d, the hair cuticle;
e, the outer root sheath; f, the inner root sheath; g, the
papilla from which the hair is growing; h, a sebaceous gland; i, a
sudoriferous gland.

THE SEBACEOUS GLANDS are small saccular glands with their ducts opening into the
mouths of the hair follicles. They furnish a natural lubricant to the hairs and the
skin.

THE SUDORIFEROUS OR SWEAT GLANDS are composed of coiled tubes which lie in the
deeper portion of the skin, and send up a corkscrew-like duct to open on the surface
of the epidermis. They are numerous over the whole of the body.

FIG. 25.—LONGITUDINAL SECTION THROUGH NAIL AND NAIL-BED OF A HUMAN FOETAL
FINGER.[A] a, The nail; b, the rete mucosum; c, the longitudinal
ridges of the corium.

[Footnote A: Seeing that the section is a longitudinal one, it would appear from
the way the ridges cut that they are running transversely beneath the nail. Their
extreme delicacy, however, prevents a single one showing itself along the length of
the section, and their constant accidental cutting makes them appear to run
transversely (H.C.R.).]

THE HUMAN NAILS are thickenings of the lowermost layer of the horny portion of the
epidermis, the stratum lucidum. They are developed over a modified portion of the
corium known as the nail-bed. The horny substance of the nail is composed of clear
horny cells, and rests immediately upon a Malpighian layer similar to that found in
the epidermis generally. Instead of the papillæ present elsewhere in the skin,
the corium of the nail-bed is marked by longitudinal ridges, a similar, though less
distinct, arrangement to that found in the laminæ of the horse’s foot.

Having thus paved the way, we are now in a better position to discuss our original
question (Are the horny laminæ secreted by the sensitive?), and better able to
appreciate the work that has been done towards the elucidation of the problem.

A most valuable contribution to this study is an article published in 1896 by
Professor Mettam.[A] Here the question is dealt with in a manner that must
effectually silence all other views save such as are based upon similar methods of
investigation—namely, histological examination of sections of equine hoofs in
various stages of foetal development.

[Footnote A: The Veterinarian, vol. lxix., p.1.]

Professor Mettam commences by drawing attention to the error that has been made in
this connection by studying the soft structures of the foot separated by ordinary
putrefactive changes from the horny covering. “In this way,” the writer points out,
“a wholly erroneous idea has crept in as to the relation of the one to the other, and
the two parts have been treated as two anatomical items, when, indeed, they are
portions of one and the same thing. As an illustration, and one very much to the
point at issue, the soft structures of the foot are to the horny covering what the
corium of the skin and the rete Malpighii are to the superficial portions of the
epidermis. Indeed, the point where solution of continuity occurs in macerating is
along the line of the soft protoplasmic cells of the rete.”

In the foregoing description of the skin we have seen that the corium is not a
plane surface, but that it is studded by numerous papillary projections, and
that these projections, with the depressions between them, are covered by the cells
of the epidermis.

The corium of the horse’s foot, however, although possessed of papillæ in
certain positions (as, for example, the papillæ of the coronary cushion, and
those of the sensitive frog and sole), has also most pronounced ridges (laminæ)
which run down the whole depth of the os pedis. Each lamina again carries ridges
(laminellæ) on its lateral aspects, giving a section of a lamina the appearance
of being studded with papillæ. We have already pointed out the ridge-like
formation of the human nail-bed, and noted that, with the exception that the
secondary ridges are not so pronounced, it is an exact prototype of the laminal
formation of the corium of the horse’s foot.

The distribution of the laminæ over the foot we have discussed in the
chapter devoted to the grosser anatomy. In a macerated foot the sensitive
laminæ of the corium interdigitate with the horny laminæ of the hoof;
that is to say, there is no union between the two, for the simple reason that it has
been destroyed; they simply interlock like the unglued junction of a finely
dovetailed piece of joinery. But no further, however, than the irregularities of the
underneath surface of the epidermis of the skin can be said to interlock with the
papillæ of the corium does interlocking of the horny and sensitive laminæ
occur. It is only apparent. The horny laminæ are simply beautifully regular
epidermal ingrowths cutting up the corium into minute leaf-like projections.

In a macerated specimen, then, the exposed sensitive structures of the foot
exhibit the corium as (1) the Coronary Cushion, fitting into the cutigeral
groove; (2) the Sensitive Laminæ, clothing the outer surface of the
terminal phalanx, and extending to the bars; (3) the Plantar Cushion, or
sensitive frog; and (4) the Sensitive Sole.

The main portion of the wall is developed from the numerous papillæ covering
the corium of the coronary cushion. We have in this way numberless down-growing tubes
of horn. Professor Mettam describes their formation in a singularly happy fashion:
“Let the human fingers represent the coronary papillæ, the tips of the fingers
the summits of the papillæ, and the folds of skin passing from finger to finger
in the metacarpo-phalangeal region the depressions between the papillæ. Imagine
that all have a continuous covering of a proliferating epithelium. Then we shall have
a more or less continuous column of cells growing from the tip of the finger or
papilla (a hollow tube of cells gradually moving from off the surface of the finger
or papilla like a cast), and similar casts are passing from off all the fingers or
papillæ.”

From this description it will be noticed that each down-growing tube of horn bears
a striking resemblance to the growth of a hair, described on p. 47. In fact, the horn
tube may be regarded as what it really is, a modified hair.

We next continue Professor Mettam’s illustration, and note how the modified hairs
or horn tubes become as it were matted together to form the hoof wall. The cells
lining the depressions are also proliferating, and their progeny serve to cement
together the hollow casts of the papillæ, thus giving the inter-tubular
substance. We have thus produced hollow tubes, united together by cells, all arising
from the rete Malpighii of the coronary corium. Section of the lower part of the horn
tubes shows them to contain a cellular debris.

Thus, in all, in the horn of the wall we find a tubular, an intertubular, and
intratubular substance. In fact, hairs matted together by intertubular material, and
only differing from ordinary hairs in their development in that they arise, not from
papillæ sunk in the corium, but from papillæ projecting from its
surface.

Although this disposes of the wall proper, there still confronts us the question
of the development of the horny laminæ. To accurately determine this point it
is absolutely essential to examine, histologically, the feet from embryos.

In the foot of any young ungulate in the early stages of intra-uterine life
horizontal sections will show a covering of epidermis of varying thickness.[A] This
may be only two or three cells thick, or may consist of several layers. Lowermost we
find the cells of the rete Malpighii. As some criterion of the activity with which
these are acting, it may be noted that with the ordinary stains their nuclei take the
dye intensely. The cells of this layer rest upon a basement membrane separating the
epidermis from the corium. At this stage the corium has a perfectly plane
surface.

[Footnote A: Equine foetus, seventy-seven days old.]

FIG. 26.—SECTION OF FOOT OF EQUINE FOETUS, SEVENTY-SEVEN DAYS OLD. The rete
Malpighii rests on a plane corium; the rent in the section is along the line of the
cells of the rete (Mettam).

FIG. 27.—SECTION FROM FOOT OF SHEEP EMBRYO. It shows a pronounced epithelial
ingrowth into the corium (Mettam).

The next stage will demonstrate the first step in the formation of the sensitive
laminæ.[A] The plain surface of the corium has now become broken up, and what
is noticed is that the broken-up appearance is due to the epithelial cells irrupting
and advancing en échelon into its connective tissue. Each point of the
ingrowing lines of the échelon has usually one cell further advanced
into the corium than its neighbours, and may be termed the apical cell. The
fine basement membrane separating epithelium from corium is still clearly evident.
This epidermal irruption of the corium takes place at definite points right round the
foot. It is extremely probable, however, that it commences first at the toe and
spreads laterally.

[Footnote A: Sheep embryo, exact age unknown.]

As yet, these cellular ingrowths (which are destined to be the horny
laminæ, and cut up the corium into sensitive laminæ) are free from
irregularities or secondary laminæ. Before these are to be observed other
changes in connection with the ingrowths are to be noticed.

FIG. 28.—SECTION FROM CALF EMBRYO. The epithelial ingrowths hang down from
the epidermis into the corium like the teeth of a comb (Mettam).

The first is merely that of elongation of the epithelial processes into the
connective tissue, until the rete Malpighii gives one the impression that it has
hanging to its underneath surface and into the corium a number of thorn-like
processes. These extend all round the front of the foot, and even in great part
behind. Accompanying this elongation of the processes is a condensation of the
epithelial cells immediately above the rete Malpighii, with a partial or total loss
of their nuclei. This is the first appearance of true horn, and its commencement is
almost coincident with the first stages of ossification of the os pedis.

FIG. 29.—SECTION OF AN EPITHELIAL INGROWTH FROM AN EQUINE FOETUS. It shows
commencing secondary laminar ridges. In the centre are epithelial cells which are
undergoing change into horny elements to form the horn core, or ‘horny laminæ’
(Mettam).

With the appearance of horn comes difficulty of sectioning. The last specimen that
Professor Mettam was able to satisfactorily cut upon the microtome was from a foetus
between three and four months old. In this the secondary laminar ridges were clearly
indicated, and the active layer of the rete Malpighii could be traced without a break
from one ingrowing epithelial process to the next, and around this, following all the
irregularities of its outline, and covering the branches of the nascent laminæ.
The laminæ mostly show this branching as if a number of different growing
points had arisen, each to take on a function similar to the epithelial process as it
at first appeared.

In the centre of the processes a few nuclei may be observed, but they are scarce,
and stain only faintly; they have arisen from the cells of the rete Malpighii which
have grown into the corium. In fact, the active cells are passing their daughters
into the middle of the process, and these pass through similar stages as those
derived from the ensheathing epidermis. In other words, the daughter cells of the
constituents of the rete Malpighii which have grown into the corium pass through a
degeneration precisely similar to that undergone by cells shed at desquamation, or
those which eventually give rise by their agglutination to a hair.

This is the real origin of the horny laminæ, and the thickness of these is
increased merely by an increase in the area covered by the cells of the rete
Malpighii—i.e., by the development of secondary laminar ridges. If a
section from a foal at term be examined, the processes will be found far advanced
into the corium, and, occupying the axis of each process, will be seen a horny plate,
continuous with the horn of the wall. No line of demarcation can be observed between
the horn so formed and the intertubular material of the wall. They merge into and
blend with each other, with no indication of their different origins. The cells that
have invaded the corium have thus not lost their horn-forming function. There
has merely been an increase in the area for horn-producing cells. The horny processes
are continuous with the hoof proper at the point where the epithelial ingrowth first
commenced to invade the corium, and fuses here with the horn derived from the cells
of the rete Malpighii which have not grown inwards, and which are found
between the processes in the intact foot. From this it is clear that some
considerable portion of the horn of the wall is derived from the cells of the rete
Malpighii covering the corium of the foot. It becomes even more clear when we
remember the prompt appearance of horn in cases where a portion, or the whole, of the
wall has been removed by operation or by accident (see reported cases in Chapter
VII.).

The activity of the cells of the rete Malpighii of the corium covering the
remainder of the foot will be quite as necessary as the activity of the cells of the
coronary papillæ which form the horn tubes themselves. ‘For,’ in Professor
Mettam’s own words, ‘I am inclined to believe that much of the “white line” which is
found uniting the wall of the hoof to the sole has been derived from the horn formed
from the rete of the foot corium. This origin will explain the absence of pigment
from this thin uniting “line,” as it does from the horn lining the interior of the
wall. The cells of the rete are free of colouring matter.’

FIG. 30.—SECTION THROUGH HOOF AND SOFT TISSUES OF A FOAL AT TERM. The horn
of the wall is shown, and the horn-core (‘horny laminæ’) of the epithelial
ingrowth. The latter has advanced far into the corium, and is now provided with
abundant secondary laminar ridges (Mettam).

From the matter here given us it is easy to understand how, in a macerated foot,
the appearance is given of interlocking of the sensitive and horny laminæ. We
see that the horny laminæ are ingrowths of the rete Malpighii, ploughing into
and excavating the corium into the shape of leaves—the sensitive laminæ.
Putrefactive changes simply break into two separate portions what originally was one
whole, by destroying the cells along its weakest part. This part is the line of soft
protoplasmic cells of the rete Malpighii. Thus the more resistant parts (the horn on
the one hand, and the corium covering the foot on the other) are easily torn
asunder.

As a result of the evidence we have quoted, we are able to answer our original
question in the affirmative. Seeing that the horny and the sensitive laminæ are
both portions of the same thing—namely, a modified skin, in which the epidermis
is represented by the horny laminæ, and the corium by the sensitive—it is
clear to see that the cells covering the inspreading horny laminæ are dependent
for their growth and reproduction upon the cells with which they are in immediate
contact—namely, those of the sensitive laminæ—and that therefore
the sensitive laminæ are responsible for the growth of the horny.

B. CHEMICAL PROPERTIES AND HISTOLOGY OF HORN.

Horn is a solid, tenacious, fibrous material, and its density in the hoof varies
in different situations. It is softened by alkalies, such as caustic potash or soda
and ammonia, the parts first attacked being the commissures, then the frog, and
afterwards the sole and wall. Strong acids, such as sulphuric acid and nitric acid,
also dissolve it.

The chemical composition of the hoof shows it to be a modification of albumin, its
analysis yielding water, a large percentage of animal matter, and materials soluble
and insoluble in water. The proportions of these, as existing in the various parts of
the hoof, have been given by Professor Clement as follows:

Horn appears to be identical with epidermis, hair, wool, feathers, and whalebone,
in yielding ‘keratin,’ a substance intermediate between albumin and gelatine, and
containing from 60 to 80 per cent. of sulphur.

That horn is combustible everyone who has watched the fitting of a hot shoe knows.
That it is a bad conductor of heat, the absence of bad after-effects on the foot
testifies.

FIG. 31.—PERPENDICULAR SECTION OF HORN OF WALL.

In a previous page we have described the manner of growth of the horn tubules, and
noted the direction they took in the wall; also, we have noticed the existence
between them of an intertubular horn or cement.

Those who wish to give this subject further study will find an excellent series of
articles by Fleming in the Veterinarian for 1871. We shall content ourselves
here with introducing one or two diagrams and photo-micrographs, and dealing with the
histology very briefly.

Under the microscope the longitudinal striation of the wall is found to be due to
the direction taken by the horn tubules.

Fig. 31 is a magnified perpendicular section of the wall. In it the parallel dark
striæ are the horn tubules in longitudinal section. The lighter striæ
represent the intertubular material.

Fig. 32 gives us the wall in horizontal section. To the left of this picture we
find the horn tubules cut across, and standing out as so many concentrically ringed
circles. In the centre of the figure are seen the horny laminæ, with their
laminellæ, and the sensitive laminæ. The right portion of the figure
pictures the corium.

FIG. 32.—HORIZONTAL SECTION OF HORN OF WALL.

Fig. 33 is, again, a horizontal section, cut this time at the junction of the wall
with the sole. To the left are seen, again, the horn tubules of the wall, and to the
centre the horny laminæ. In this position, however, the structures
interdigitating with the horny laminæ are not sensitive, but are themselves
horny. As the diagram shows, they contain regularly arranged horn tubules cut across
obliquely. It is this horn which forms the ‘white line.’ To the extreme right of the
figure are seen the horn tubules of the sole.

There remains now but to notice the arrangement of the horn tubules in the frog.
The peculiar, indiarubber-like toughness of this organ is well known. Histological
examination gives a reason for this.

FIG. 33.—HORIZONTAL SECTION OF HORN THROUGH THE JUNCTION OF THE WALL WITH
THE SOLE. a, Horn tubule of the wall; b, horn tubule of the sole; c,
d, horny laminæ.

FIG. 34.—SECTION OF FROG THROUGH CORIUM AND HORN. The long finger-like
projections of corium into epidermis are sections of the long papillæ from
which the horn-tubes of the sole grow. In the stainable portion of the epidermis are
to be clearly seen light and dark streaks pointing out the alternate strata-like
arrangement of cells mentioned in the text (Mettam).

The horn tubules of the frog are sinuous in their course. This is accounted for by
the fact that in the horn of the frog there is a large amount of intertubular
material, this having the effect of frequently turning the horn tubules from the
straight. In addition to this, the intertubular material has a peculiar arrangement
of the cells composing it. These are laid down in alternating striæ (1) of
cells with their long axes longitudinal, and (2) of cells with their long axes
horizontal. This is seen in Fig. 34, between the long papillæ of the corium,
where the lines of longitudinally arranged cells in horizontal section stand out
darker than the adjoining strata in which their arrangement is horizontal. The
tortuous direction of the horn tubules, and the almost interlocking nature of the
alternating strata of the intertubular material, together combine to give the frog
its characteristic toughness and resiliency.

C. EXPANSION AND CONTRACTION OF THE HOOF.

Among other questions productive of heated argument come those relating to
expansion of the horse’s hoof. In the past many observers have strenuously insisted
on the fact that expansion and contraction regularly occur during progression.
Opposed to them have been others equally firm in the belief that neither took place.
Quite within recent times this question also has been settled once and for all by the
experiments of A. Lungwitz, of Dresden. His conclusions were published in an article
entitled ‘Changes in Form of the Hoof under the Action of the Body-weight.'[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. iv.,
p. 191. The whole of the matter in this article, from which we have borrowed Figs. 35
and 36, is too long for reproduction here. It forms, however, most instructive
reading, and its careful perusal will well repay everyone interested in this most
important question (H.C.R.).]

In connection with this it is interesting to note how, all unconsciously, two
separate observers were simultaneously arriving by almost identical means at an
equally satisfactory answer to the question. Prior to the publication of Lungwitz’s
article on the subject, Colonel F. Smith, A.V.D., had arrived at similar conclusions
by working on the same methods.

Fig. 35. I. Electric Bell with Dry Element. a, Under part, with box, for the dry
element; 6, roller for winding up the conducting-wires; c, dry element, with
screw-clamp for attachment of the conducting-wires; c’, conducting-wire leading to
the screw-clamp, with contact-spring in c’, Fig. 2, or to the wall in Fig. 3; d,
upper part, with bell; d’, conducting-wire to the shoe d’ in Figs. 2 and 3; e, strap
for slinging the apparatus around the body of the assistant or rider; f,
connecting-wire between bell and dry element.

Fig. 35. II. Hoof Shod with Shoe provided with Toe-piece and Calkins; Wall of the
Hoof covered with Tinfoil. a, Heel angle, with b, the contact-screws; c, screw-clamp,
with contact-spring (isolated from the shoe); c’ conducting-wire from the same; d,
screw-clamp, with conducting-wire (d’) screwed into the edge of the shoe; e, nails
isolated by cutting a small window in the tinfoil.

Fig. 35. III. Hoof Shod with Plain Shoe; Horny Wall covered with Tinfoil. a, Toe
and heel angle, with b, the contact-screws; c, conducting-wire passing from the
tinfoil on the wall; d, conducting-wire passing from the shoe; c’, d’, ends of the
conducting-wires, which must be imagined connected with the ends c’, d’, passing from
the apparatus.

It is unnecessary for our purpose here to minutely describe the exact modus
operandi of these two experimenters. Briefly, the method of inquiry adopted in
each case was the ‘push and contact principle’ of the ordinary electric bell, and the
close attention which was paid to detail will be sufficiently gathered from Figs. 35
and 36.

Fig. 36. I. LEFT FORE-FOOT SHOD AND MOUNTED TO RECOGNISE THE SINKING OF THE SOLE.
a, Iron plate covering the inner half of the horny sole; b, openings in
the same, with screw-holes for the reception of the contact-screw c (the part
of the sole under the plate is covered with tinfoil, which at d passes out
under the outer branch of the shoe, and becomes connected with the tinfoil of the
wall; in order to give the freshly applied tinfoil a better hold, copying-tacks are
at e passed through it into the horn, and one is similarly used to protect the
tinfoil at the place where the contact-screw touches the latter); f, holes
with screw thread for the fastening of the angle required to measure the movement of
the wall, and also for the fastening of the conducting-wire, g; h,
conducting-wire passing from the tinfoil; i, isolated nails.

Fig. 36. II. BAR-SHOE WITH OPENINGS. a, Near the inner margin and in the
longitudinal bar; b, for the reception of the contact-screw c; d,
openings for fastening the angle and the conducting-wires.

After numerous experiments with the depicted contact-screws, moved to the various
positions indicated in the drawings, the following conclusions were arrived at:

1. BEHAVIOUR OF THE CORONARY EDGE.—During uniform weighting of all four
hoofs the coronary edge shows a tendency to contraction in the anterior and lateral
regions of the hoof, and a tendency to expansion posteriorly. With heavy weighting of
the hoof, which is shown by a backward inclination of the fetlock, contraction in the
anterior and lateral regions is slight, but the expansion behind, in the region of
the heels, is distinct, commencing gradually in front, becoming stronger, and
diminishing again posteriorly. The coronary edge of the heels becomes slightly bulged
outwards. The bulbs of the heels swell up and incline a little backwards and
downwards.

When the fetlock is raised the expansion of the coronary edge of the heels
disappears from behind forwards, passing forwards like a fluid wave. In the lateral
and anterior regions of the coronary edge the contraction disappears; and when the
weight is thrown off the foot it passes into a gentle expansion of the coronary edge
of the toe. During the opposite movement of the fetlock, that of sinking backwards,
this change of form is executed in the converse manner.

In short, the coronary edge resembles a closed elastic ring, which yields to
pressure, even the most gentle, of the body-weight, in such a way that a bulging out
of any one part is manifested by an inward movement of another part.

In Fig. 37, b, the dotted line represents the changes of form in
comparatively well-formed and sound hoofs at the moment of strongest
over-extension[A] of the fetlock-joint.

[Footnote A: The term ‘over-extension,’ as employed by Lungwitz, is intended to
indicate that position assumed by the fetlock-joint when the opposite foot is raised
from the ground.]

2. BEHAVIOUR OF THE SOLAR EDGE.—Under the action of the body-weight this is
somewhat different from that of the coronary edge. Anteriorly, and at the sides, as
far as the wall forms an acute angle with the ground, the tendency to expansion
exists, but the change of form first becomes measurable in the region where the
lateral cartilages begin. Quite posteriorly the expansion again diminishes.

Fig. 37, a, by the dotted line represents the expansion at the moment of
over-extension of the fetlock-joint. This expansion is itself rather less than at the
coronary edge, and it shows itself distinctly only when the weighted hoof is
exposed to a counter-pressure on the sole and frog, no matter whether the
counter-pressure is produced naturally or artificially. Thus anything tending to the
removal of the pressure from below, such as a decayed condition of the frog or
excessive paring in the forge, will diminish the extent of expansion of the solar
edge.

Contraction of the solar edge of the heels occurs at the moment of greatest
over-extension of the fetlock-joint—that is, in a foot with pressure from below
absent. On the face of it, this appears impossible. Lungwitz, however, has perfectly
demonstrated it; and, when dealing with the functions of the lateral cartilages in a
later paragraph, we shall show reason for why it is but a simple and natural result
of the foot dynamics.

3. BEHAVIOUR OF THE SOLE.—The horny sole becomes flattened under the action
of the body-weight. This is most distinct at the solar branches, and gradually shades
off anteriorly and towards the circumference. As might be supposed, width of hoof and
thickness of the solar horn exert an influence on the extent of this movement. The
sinking of the horny sole is most marked in flat hoofs.

D. THE FUNCTIONS OF THE LATERAL CARTILAGES.[A]

We have just referred to contraction of the heels as taking the place of a normal
expansion in those cases where ground frog-pressure was absent. We shall readily
understand this when we bear in mind the anatomy of the parts concerned, especially
that of the plantar cushion. This wedge-shaped structure we have already described as
occupying the irregular space between the two lateral cartilages, the extremity of
the perforans tendon, and the horny frog.

Now, when weight or pressure is exerted from above on to this organ, and the
frog is in contact with the ground below, it is clear from the position the
cushion occupies that, whatever change of form pressure from above will cause it to
take, it must certainly be limited in various directions.

FIG. 37. a, The dotted lines in this diagram represent the expansion of the
solar edge of the hoof at the moment of over-extension of the fetlock-joint;
b, the dotted line represents the change in form of the coronary edge under
similar circumstances.

Because of the shape of the cushion its change of form cannot be forwards
(simultaneous pressure from above and below on to this wedge with its apex forwards
must tend to give it a backward change of form). Because of the pastern being
horizontal, and aiding in the downward pressure, its change of form cannot be
upwards. And because of the ground it cannot be downwards. It follows, therefore,
that the movement must be backwards and outwards, being especially directed outwards
because of its shape and the median lacuna in its posterior half—this latter,
the lacuna, accommodating as it does the frog-stay, preventing the tendency to
backward movement becoming excessive, and directing the change of form to the sides.
Where the greatest pressure is transmitted, then, is to the inner aspects of the
flexible lateral cartilages. The coronary cushion being continuous with the plantar,
the backward and outward movements of the latter will tend to pull upon and tighten
the former, especially in front. This will account for the contraction noted
by Lungwitz in the anterior half of the coronary edge of the hoof.

Remove the body-weight, and naturally the elastic nature of the lateral cartilages
and the coronary and plantar cushions, with, in a less degree, that of the hoof,
cause things to assume their normal position.

Repeat the weighting of the hoof, in this second case without
frog-pressure, and we shall see at once that we have done away with one of the
greatest factors in determining the outward and backward movements of the plantar
cushion—namely, the pressure from below on its wedge-shaped mass. The movement
of the plantar cushion will now be downwards as well as backwards; and, seeing
that it is attached to the inner aspect of each lateral cartilage, we shall expect
these latter, by the downward movement of the plantar cushion, to be drawn
inwards. This Lungwitz has shown to occur.

The chief function of the lateral cartilages, therefore, is to receive the
concussion engendered by locomotion, which concussion is directed backwards and
outwards by the pad-like plantar cushion.

In addition to this, the lateral cartilages, together with the plantar and
coronary cushions, play the part of a valve to the whole of the veins of the
foot.

It is in this way: We have only to refer to the chapter on anatomy to see that the
whole of the foot is covered with a tissue of extreme vascularity. Thus we find
papillæ—the over the coronary cushion; enlarged and modified
papillæ sensitive laminæ—covering the anterior face of the os
pedis; and numberless papillæ again covering the sole. There can be no doubt
that the quantity of fluid brought by the bloodvessels of these papillæ to the
foot acts largely as a means of hydraulic protection to the soft structures.[A] In
like manner as that delicate organ, the brain, is best protected by being floated
upon the cerebro-spinal fluid and bloodvessels (which fluids transmit waves of
concussion or pressure through the organ without injury to the delicate cells
forming it), so, in like manner, does the extreme vascularity of the foot protect the
cells of its softer structures from the effects of pressure and concussion.

[Footnote A: The Veterinary Record, vol. iii., p. 518.]

That this law of hydraulics may operate in the horse’s foot to the best

advantage, the veins must be provided with valves, and valves of no mean strength.
These we know to be absent. It is here that the lateral cartilages and the elastic
substances of the coronary and plantar cushions step in to supply the deficiency.

At the time when weight is placed upon the foot (with, of course, a tendency to
drive the blood upwards in the limb), and, therefore, the time when a valvular
apparatus is needed to retain the fluid in the foot, we find the wanting conditions
supplied by the pressure outwards of the plantar cushion compressing the large
plexuses of veins on each side of the lateral cartilages, to which plexuses, it will
be remembered, the bulk of the venous blood from the foot was directed. A more
perfect valvular apparatus, automatic and powerful, it would be difficult to
imagine.

E. GROWTH OF THE HOOF.

We will conclude this chapter with a few brief remarks on the growth of the hoof.
That the rate of growth is slow is a well-known fact to every veterinarian, and it
will serve for all practical purposes when we state that, roughly, the growth of the
wall is about 1/4 inch per month. This rate is regular all round the coronet, from
which it follows that the time taken for horn to grow from the coronary edge to the
inferior margin will vary according as the toe, the quarters, or the heels are under
consideration.

As might naturally be expected, the rate of growth will depend on various
influences. Any stimulus to the secreting structures of the coronet, such as a
blister, the application of the hot iron, or any other irritant, results in an
increased growth. Growth is favoured by moisture and by the animal going unshod, as
witness the effects of turning out to grass. Exercise, a state of good health,
stimulating diets—in fact, anything tending to an increased circulation of
healthy blood—all lead to increased production of horn. With the effects of
bodily disease and of ill-formed legs and feet on the wear of the hoof, and the
growth of horn, we shall be concerned in a future chapter.

CHAPTER IV

METHOD OF EXAMINING THE FOOT

As a general rule, it may be taken that most diseases of the foot are
comparatively easy of diagnosis. When, however, the condition is one which commences
simply with an initial lameness, the greatest care will have to be exercised by the
practitioner.

What remarks follow here should rightly be confined to a treatise on lameness.
This much, however, we may state: As compared with lameness arising from abnormal
conditions in other parts of the limb, that emanating from abnormalities of the foot
is easy of detection. With a case of lameness before him, concerning which he is in
doubt, the practitioner remembers that a very large percentage may safely be referred
to the foot, and, if wise, subjects the foot to a rigorous examination.

Much may be gathered by first putting the animal through his paces. When at a
trot, notice the peculiarity of the ‘drop,’ whether any alteration in going on hard
or soft ground, and watch for any special characteristic in gait. At the same time
inquiry should be made as to the history of the case; its duration; whether pain, as
evidenced by lameness, is constant or periodic; the effect of exercise on the
lameness; and the length of time elapsed since the last shoeing.

This failing to reveal adequate cause for the lameness in any higher part of the
limb, one is led, by a process of negative deduction, to suspect the foot. If
‘pointing’ is a symptom, its manner is noticed. The foot is compared with the other
for any deviation from the normal. In some cases the two fore or the two hind feet
may differ in size. Though this may not necessarily indicate disease, it may,
nevertheless, be taken into account if the lameness is not easily referable to any
other member. Measurement with calipers will then be of help, and a pronounced
increase in size, especially if marked in one position only, given due consideration.
The hand is used upon each foot alternately to look for change of temperature, to
detect the presence of growths small enough to escape the eye, and to discover
evidence of painful spots along the coronet.

At this stage the method of percussion recommends itself, and in many cases no
more useful diagnostic agent is to be found than the ordinary hammer. As a
preliminary, the foot of the sound limb should be always tapped first. This
precaution will serve to bring to light what is frequently met with—the
aversion nervous animals sometimes exhibit to this manner of manipulation of the
hoof. Unless this is done, the ordinary objection to interference is apt to be read
as evidence of pain. No aversion to the method being shown, the suspected foot is
gently tapped in various places round the wall, a keen look-out being kept for any
manifestation of tenderness. This may vary from a slight resentment to each tap,
indicated by a sudden lifting and setting down again of the foot, to a complete
removal of the foot from the ground, and a characteristic pawing of the air that
points out clearly enough the seat of pain.

Evidence of pain once given, the tapping is persisted in until, in some cases, the
exact position of the tender spot is definitely located.

Failing evidence obtained from percussion, attention should next be given to the
shoeing. We may add here that, even when difficulties have to be encountered in doing
it, it is always a wise plan to have the shoe removed.

The nails should be removed one by one, the course they have taken, their point of
emergence on the wall, and the condition of their broken ends all being carefully
noted as they are withdrawn.

The removed shoe should next be examined as to the coarseness or fineness of its
punching and the ‘pitch’ of its nail-holes, and close attention given to the shape of
its bearing surface.

From that we may pass to a consideration of the underneath surface of the foot.
The drawing-knife should be run lightly over the whole of its surface, the first
thing to be noticed being the point of entrance of the nails as compared with the
coarseness or fineness of the punching, and the staining or otherwise of the horn
immediately around. We may thus be guided towards mischief arising from tight nailing
apart from actual prick of the foot.

This done, more than usual care should be taken in following up any other small
prick or dark spot that may show itself upon the white surface of the cleaned sole.
In any case, a suspicious-looking speck should be followed up with the searcher until
it is either cut out or is traced to the sensitive structures.

While this is done, we should also have noticed the condition of the horn at the
seat of corn; should have noticed the shape of the heels, contracted or otherwise;
and the appearance of the frog, clean or discharging.

A point to be remembered in making this exploratory paring of the foot is the
peculiar consistency of the horn of the frog, and its tendency to hide the existence
of punctures. In like manner, as a pin pierces a piece of indiarubber, and leaves no
clearly visible trace of the hole it has made, so does a nail or other sharp object
penetrate the frog, leaving but little to show for the mischief that has been
done.

After all, even though we may have fully decided the foot is at fault, our case of
lameness may remain obscure so far as a cause is concerned. Nothing remains, then,
but to acknowledge the inability to discover it, to advocate poulticing, or some
other expectant palliative measure, and to bring the case up for further examination
at no distant date. Where, though we may have suspected the foot, we have not been
able to definitely assure ourselves that there the mischief is to be found, a further
method of examination presents itself—namely, subcutaneous injections of
cocaine along the course of the plantar nerves.

The salt of cocaine used is the hydrochlorate, 2-1/2 grains for a pony, 4 grains
for a medium-sized animal, and 6 grains for a large horse. A solution of this is made
in boiled water (about 3 drams), and injected at the seat of the lower operation of
neurectomy.

It is advisable to first render aseptic the seat of operation, and to sterilize
both the needle and the syringe by boiling. A suitable point to choose for the
injection is exactly over the upper border of the lateral faces of the two sesamoids,
the needle being introduced behind the cord formed by the nerve and accompanying
vessels, and parallel with it.

It is possible that the vein or the artery may be wounded, but such accident is of
little importance. All that is necessary in that case is to partly withdraw the
needle and again insert it. It is advisable to use a twitch.

When the needle is in position, the injection should be made slowly, and at the
same time the point of the needle should be made to describe a semicircular sweep, so
as to spread the solution over as wide an area as is possible.

Anæsthesia ensues in from six to twenty minutes, and if the cause of the
lameness is below the point of injection the animal moves sound.

Regarding this method of diagnosis, Professor Udriski of Bucharest, after a series
of trials, sums up as follows:

1. For the diagnosis of lameness cocaine injections are of very considerable
value.

2. These injections should be made along the course of the nerves.

3. Solutions heated to 40° or 50° C. produced quicker, deeper, and longer
anæsthesia than equally strong cold solutions.

4. In the sale of horses cocaine injections conceal fraud.

Cocaine being an irritant, it must be remembered that after the anæsthesia
the lameness is somewhat more marked than before.

To the cocaine other practitioners add morphia in the following proportions:

As a diagnostic this mixture of the two is said to be far superior to either
cocaine or morphia alone.

In connection with this subject, Professor Hobday has published, among others, the
following cases illustrating the practical value of this method of diagnosis:[A]

[Footnote A: The Journal of Comparative Pathology and Therapeutics vol.
viii., pp. 27, 43.]

CASE I.—Cab gelding. Seat of lameness somewhat obscure; navicular disease
suspected. Injected 2 grains of cocaine in aqueous solution on either side of the
limb, immediately over the metacarpal nerves.

Five Minutes.—Lameness perceptibly diminished.

Ten Minutes.—Lameness scarcely perceptible.

CASE II.—Mare. Obscure lameness; foot suspected. Injected 30 minims of a 5
per cent. solution on either side of the leg just above the fetlock.

Ten Minutes.—No lameness, thus proving that the seat of lameness was
below the point of injection.

CASE III.—Cab gelding, aged, free clinique; Messrs. Elme’s and Moffat’s
case. Obscure lameness; foot suspected of navicular disease; very lame. Injected 30
minims of a 5 per cent. solution of cocaine on either side of the leg over the
metacarpal nerves.

Six Minutes.—Lameness perceptibly less; there was no response
whatever on the inside of the leg to the prick of a pin. On the outside, which had
not been injected so thoroughly, there was sensation, although not so much as in a
healthy foot.

Ten Minutes.—Lameness had almost disappeared; so much so, that the
opinion as to navicular disease was confirmed, and neurectomy was performed.
Immediately after this operation there was no lameness whatever.

The same author also reports numerous cases among horses and cattle, dogs and
cats, pointing out the toxic properties of the drug. The symptoms following an
overdose are interesting enough to relate here, and I select the following case of
Professor Hobday’s as being fairly typical:[A]

[Footnote A: Loc. cit.]

CASE IV.—Cart gelding. Free clinique; navicular disease. Injected
subcutaneously over the metacarpal nerves on each side 6 grains of cocaine in aqueous
solution. During the operation the animal manifested no signs of pain whatever, not
even when the nerve was cut. This animal received altogether 12 grains of cocaine (3
grains were given on either side first, then fifteen minutes afterwards the same dose
repeated). The effect was manifested on the system in ten minutes after the second
injection by clonic spasms of the muscles of the limbs (the legs being involuntarily
jerked backwards and forwards at intervals of about twenty seconds), which materially
interfered with the performance of the operation. The animal was also continually
moving the jaws, and was very sensitive to sounds, moving the ears backwards and
forwards. This hyperæsthesia, as evinced by the movement of the ears, lasted
for some considerable time after the animal had been allowed to get up.

Cocaine hydrochlorate solutions, if intended to be kept for any length of time,
should have added to them when freshly made 1/200 part of boric acid in order to
preserve them. Even then they are liable to spoil, and should, for subcutaneous
injection, be made up just before needed for use.

CHAPTER V

GENERAL REMARKS ON OPERATIONS ON THE
FOOT

A. METHODS OF RESTRAINT.

Many of the simple operations on the foot, such as the probing of a sinus, the
paring out of corns, or the searching of pricks, may most suitably be performed with
the animal’s leg held by the operator as a smith holds it for shoeing. According to
the temperament of the animal, even the operation for the removal of a portion of the
sole, or the injection of sinuses with caustics, may be carried out with the animal
simply twitched.

When the operation is still a simple one, casting inconvenient or impossible, and
the animal restive, the twitch must be supplemented by some other method. The most
simple and one of the most effective is the blind, cap, or bluff (Fig. 38). With it
the most vicious animal or the most nervous is in many instances either cowed into
submission or soothed into quietness.

At the same time, more forcible means than the operator’s own strength must be
taken to hold the animal’s foot from the ground. If the foot is a fore-foot, and the
point desired to be operated on is to the outside, the pastern should be firmly
lashed to the forearm by means of a thin, short cord, or a leather strap and buckle.
Much may then be done in the way of paring and probing that would otherwise be
impossible.

Fig. 38—The BLIND.

Fig. 39—THE SIDE-LINE.

If the foot is a hind one, one of the many methods of using what is termed by
Liautard, in his ‘Manual of Operative Veterinary Surgery,’ the plate-longe, must be
adopted. This, in its most useful form, is a length of closely-woven cotton webbing,
from about 2 to 2-1/2 inches wide, and from 5 to 6 yards long, provided with a small
loop formed on one of its ends, and perhaps better known to English readers as a
‘side-line.’ If webbing be not available, a length of soft cotton rope, or a rope
plaited and sold for the purpose, as Fig. 39, will serve equally well. One of the
most convenient methods of using the side-line for securing the hind-foot is depicted
in Figs. 40 and 41.

FIG. 40.—THE SIDE-LINE ADJUSTED PREPARATORY TO SECURING THE NEAR
HIND-FOOT.

FIG. 41.—THE NEAR HIND-FOOT SECURED WITH THE SIDE-LINE.

Here the side-line has formed upon it a loop sufficiently large to form a collar.
This is placed round the animal’s neck, the free end of the line run round the
pastern of the desired foot, and the foot drawn forward, as in Fig. 40.

The loose end of the line is then twisted once or twice round the tight portion,
and finally given to an assistant to hold (see Fig. 41). The foot is thus held from
the ground, and violent kicking movements prevented.

Where the operation is a major one, restraint of a distinctly more forcible nature
becomes imperative. Many of the more serious operations can most advantageously be
performed with the patient secured in some form or other of stock or trevis, and the
foot suitably fixed. It is not the good fortune of every veterinary surgeon, however,
to be the lucky possessor of one of these useful aids to successful operating.
Perforce, he must fall back on casting with the hobbles (Fig. 42).

FIG. 42.—CASTING HOBBLES.

With the use of these we will assume our readers to be conversant, and will
imagine the animal to be already cast. It remains, then, but to detail the most
suitable means for firmly fixing the foot to be operated on.

Here the side-line is again brought into use. Care should previously have been
taken when casting to throw the animal so that the portion of the foot to be operated
on, whether inside or outside, falls uppermost, and that the buckle of the hobble on
that particular foot is placed so that it also is within easy reach when the animal
is down.

In the case we are illustrating the point of operation was the outside of the near
hind coronet. We will, therefore, describe the mode of fixing the near hind-foot upon
the cannon of the near fore-limb.

FIG. 43.—PHOTOGRAPH ILLUSTRATING METHOD OF ADJUSTING THE SIDE-LINE
PREPARATORY TO FIXING THE HIND-LEG UPON THE FORE.

The side-line is first adjusted as follows: It is fixed upon the cannon of the
near hind-leg (A) by means of its small loop. From there it is passed under the
forearm of the same limb, over the forearm, under the rope running from A to B; from
there over and under the thigh, to be finally brought in front of the thigh, and
below the portion of rope running from arm to thigh. The loose end of the side-line
is then given to an assistant standing behind the animal’s back, the buckle of the
hobble restraining the foot unloosed, and strong but steady traction brought to bear
from behind upon the line. The operator should now stand in front of the fore-limbs,
and, by placing a hand on the rope passing round the arm, prevent the line from
slipping below the knee.

By this means the hind-limb is pulled forward until the foot projects beyond the
cannon of the front-limb. When that position is reached, the operator grasps the hock
firmly with one hand, and, directing the side-line to be slackened, gently slides
downward the coils of rope round the arm and thigh until they encircle the cannons of
both limbs. The cannon of the hind-limb is firmly lashed to the cannon of the fore,
and the foot firmly and securely fixed in the best position for operating (see Fig.
44).

FIG. 44.—PHOTOGRAPH SHOWING THE NEAR HIND-FOOT SECURED UPON THE CANNON OF
THE NEAR FORE-LIMB.

Similarly, with the horse still on his off side, the off hind-limb may be fixed to
the near fore, and the near fore and the off fore to the near hind.

With the animal on his near side, we may fix the near hind and the off hind to the
off fore, and the off fore and near fore to the near hind.

The points to be remembered in fixing the limbs thus are: (1) The side-line should
always commence upon the cannon of the limb to be operated on; (2) it should next
pass under and over (or over and under, it is immaterial which) first the arm and
then the thigh, or the thigh and the arm, as the case may be; (3) in every case,
whether rounding the thigh and the arm from above or below, the piece of rope
completing the round should always finish below that portion preceding it, so that
traction upon it from behind the animal’s back should tend to keep all portions of it
from slipping below the knee and the hock.

With the uppermost fore-limb secured to the hind-limb in the manner we have
described, we have the underneath fore-limb suitably exposed for both the higher and
lower operations of neurectomy. The position for this operation will be made better
still if the lowermost limb (the one to be operated on) is removed from the hobbles
and drawn forward by an assistant by means of a piece of rope fastened to the
pastern.

Taking what we have described as a general guide, other modifications of thus
securing the foot will suggest themselves to the operator to meet the special
requirements of the case with which he is dealing.

Regarding the administration of chloroform, no description of the method is needed
here, as it will be found fully detailed in most good works on general surgery. Where
great immobility is needed, it is one of the most valuable means of restraint we
have. Apart from that, its use in any serious operation is always to be advocated, if
only on the score of humane consideration for the dumb animal helpless under our
hands.

B. INSTRUMENTS REQUIRED.

In addition to those required for operations on the softer structures—such
as scalpels, forceps, artery forceps, directors, scissors, etc.—the surgery of
the foot demands instruments specially adapted for dealing with the horn.

A great deal will depend upon the operator as to whether these are few or many.
The average man of resource will deem a smith’s rasp and one or two strong
drawing-knives amply sufficient, and on no account should they be omitted from the
list of those ready to hand.

FIG. 45.—THE ORDINARY DRAWING-KNIFE. The ordinary smith’s drawing-knife
(Fig. 45) is well known to almost everyone, and is well suited for much of the
rougher part of the work. The careful following up of pricks, however, and some of
the more special operations demanding removal of portions of the lateral cartilages
call for instruments of a more delicate character and peculiar construction. These
are to be found in the so-called sage-knife, and the modern (French) pattern of
drawing-knife.

FIG. 46. a, b, Modern forms of drawing-knife; c, d, e, sage-knives.
The modern drawing-knife differs from the smith’s instrument in being attached to a
straight, instead of a curved, handle, and in usually being sharp on both edges
instead of only on one. These are made in various sizes (Fig. 46, a, b), and
the blades flat, curved on the flat, or curved at an angle with the edges of the
haft.

The sage-knife, as its name indicates, is a knife with a lanceolate-shaped blade.
These also may be obtained in varying forms and sizes (Fig. 46, c, d, e). Fig.
46, c, is a single-edged, right-handed sage-knife. Fig. 46, d, is a
left-handed instrument of the same type. The double-edged sage-knife is represented
in Fig. 46, e.

FIG. 47.—SYMES’S ABSCESS-KNIFE.

It may be mentioned too, in passing, that the ordinary Symes’s abscess-knife (Fig.
47) is a most useful instrument when performing the operation of partial excision of
the lateral cartilages, its peculiar shape lending itself admirably to the niceties
of the operation.

One or two good-shaped firing-irons will also be found useful. They will lighten
the labour of tediously excavating grooves with the knife, where that procedure is
necessary; and, used in certain positions to be afterwards described, will afford
just that necessary degree of stimulus to the horn-secreting structures of the foot,
which the use of the knife alone will not.

The man in country practice will also be well advised in carrying to every foot
case a compact outfit, such as that carried by the smith. This will consist of hammer
and pincers, drawing-knife and buffer. Much valuable time is then often saved which
would otherwise be wasted in driving round for the nearest smith.

There are other special operations requiring the use of specially-devised
instruments for their successful carrying out. These we shall mention when we come to
a consideration of the operations in which they are necessary.

C. THE APPLICATION OF DRESSINGS.

One of the most common methods of applying a dressing to the foot is poulticing.
Usually resorted to on account of its warmth-retaining properties, the poultice may
also be medicated. In fact, a poultice, strongly impregnated with perchloride of
mercury or other powerful antiseptic, is a useful dressing in a case of a punctured
foot, or a wise preliminary to an operation involving the wounding of the deeper
structures. The poultice may consist of any material that serves to retain heat for
the longest time. Meal of any kind that contains a fair percentage of oil is
suitable. Crushed linseed, linseed and bran, or linseed-cake dust are among the
best.

To prepare it, all that is necessary is to partly fill a bucket with the material
and pour upon it boiling water. The hot mass is emptied into a suitable bag, at the
bottom of which it is wise to first place a thin layer of straw, in order to prevent
the bag wearing through, and then secured round the foot. This is generally done by
means of a piece of stout cord, or by straps and buckles fastened round the pastern
and above the fetlock.

An improved method of fastening has been devised by Lieutenant-Colonel Nunn:

‘A thin rope or stout piece of cord about 5 feet long is doubled in two, and a
knot tied at the double end so as to form a loop about 5 or 6 inches long, this
length depending on the size of the foot (as at A, Fig. 48). The poultice or other
dressing is applied to the foot, and the cloth wrapped round in the ordinary way, the
loop of the cord being placed at the back of the pastern (as in A, Fig. 49); the ends
of the cord are passed round, one on the inside and the other on the outside, towards
the front (as in B, Fig. 49). These ends are then twined together down as far as the
toe (see C in Fig. 49). The foot is now lifted up, and the ends of the cord (CC, Fig.
49), are passed through the loop A (as at D, Fig. 49), and then drawn tight. The ends
of the cord are now separated, and carried up to the coronet (as at EE, Fig. 49), one
on the outside, the other on the inside of the foot. They are then again twisted
round each other once or twice (as at F, Fig. 50), and are passed round the pastern
once or twice on each side. They are now passed under the cord (E, Fig. 49), and then
reversed, so as to tighten up E, and are finally tied round the pastern in the usual
manner. The arrangement of the cords on the sole is shown in Fig. 51, which is a view
from the posterior part.

FIGS. 48, 49, 50, 51.—ILLUSTRATING LIEUTENANT-COLONEL NUNN’S METHOD OF
APPLYING A POULTICE TO THE FOOT.

‘The advantages of this method of fastening have been found to be: (1) It does not
chafe the skin; (2) if properly applied it has never been known to come undone; (3)
it is the only way we know that a poultice can be satisfactorily applied to a mule’s
hind-foot; (4) horses can be exercised when the poultice is on the foot, which is
almost impossible with the ordinary leather boot; (5) the sacking or canvas does not
cut through so quickly.’

FIGS. 52, 53.—TWO FORMS OF POULTICE-BOOT.

A further method of applying the poultice is by using one of the poultice-boots
made for that purpose (see Figs. 52 and 53).

These have an objection. They are apt to be allowed to get extremely dirty, and
so, by carrying infective matter from the foot of one animal to that of another, undo
the good that the warmth of the poultice is bringing about. The advantage of the
ordinary sacking or canvas is that it may be cast aside after the application of each
poultice. Where the boot is kept clean, however, it will save a great deal of time
and trouble to the attendant.

While on the subject of poulticing, it is well to remark that in many cases it may
be more advantageous to supply the necessary warmth and moisture to the foot by
keeping it immersed in a narrow tub of water maintained at the required temperature.
By this means the warmth is carried further up the limb (sometimes an important
point), and the water can more conveniently be medicated with whatever is required
than can the poultice. In fact, it is the author’s general practice, where the
attendants can be induced to take the necessary pains, to always advise this latter
method.

FIG. 54.—SWAB FOR APPLYING MOISTURE TO THE FOOT.

Where a dressing is relied upon by some practitioners on account of the warmth it
gives, others, even in identical cases, will depend upon the effects of cold. This
may be applied by means of what are called ‘swabs.’ In their simplest form swabs may
consist only of hay-bands or several layers of thick bandage bound round the foot and
coronet, and kept cool by having water constantly poured upon them. In many cases the
form of swab depicted in Fig. 54 will be found more convenient.

When only one foot is required to be dressed, and a water-supply is available, by
far the preferable method is to attach one end of a length of rubber tubing to the
water-tap, and fasten the other just above the coronet, allowing the water to trickle
slowly over the foot. In cases where a forced water-supply is unobtainable, and the
case warrants the extra trouble, much may be done with a medium-sized cask of water
placed somewhere over the animal, and the rubber tubing connected with that.

Where the dressing is desired to be kept applied to the sole and frog only, there
is no method more satisfactory than the shoe with plates.

FIG. 55.—THE SHOE WITH PLATES. A, The plates in position; B,
the plates separated from the shoe.

FIG. 56.—THE QUITTOR SYRINGE.

The plates are of metal, preferably of thin sheet iron or zinc, and are slipped
between the upper surface of the shoe and the foot after the manner shown in Fig. 55.
The plates themselves are shaped as depicted in Fig. 55, a, b, c, a and
b curved to meet the outlines of the shoe, and c shaped so as to wedge
tightly over the posterior ends of the side plates, and between them and the shoe. A
distinct advantage of the plate method of dressing is that a certain amount of
pressure may be maintained on the sole and frog, a very important consideration in
connection with some of the diseases with which we shall later deal.

When dealing with sinuous wounds of the foot, another favourite mode of applying
dressings is by means of the syringe, and no better instrument for all cases can be
found than that known as a quittor syringe (Fig. 56).

A further mode of applying dressing, and one frequently practised in connection
with the foot, is known as ‘plugging.’ This is almost sufficiently indicated by its
name. It consists in rolling portions of the dressing into little cylinders, wrapped
round with thin paper, and introduced into a sinus or other position where considered
necessary.

D. PLANTAR NEURECTOMY.

As a last resort in the treatment of many diseases of the foot the operation of
neurectomy is often advised. It will be wise, therefore, to insert a description of
the operation here.

Derivation of the Word.—For many years the operation was known simply
as ‘nerving’ or ‘unnerving,’ and it was not until 1823, at the suggestion of Dr.
George Pearson, that Percival introduced the word neurotomy to signify the
operation with which we are now about to deal. The word neurotomy, however, used
strictly, means the act or practice of dissection of nerves, and, when applied to the
operation as practised to-day, describes only a step in the procedure.

As the operation really consists in cutting down upon, and afterwards excising a
portion of the nerve, the modern appellation of neurectomy—from the
Greek neuron, a nerve; and tome, a cutting, signifying the cutting out
of a nerve or the portion of a nerve—is far more suitable.

According as the nerve operated on is the plantar or the median, the operation is
known as plantar or median neurectomy.

History of the Operation.—It is to two English veterinarians that we
owe the introduction of the operation to the veterinary world. In 1819 Professor
Sewell announced himself as the originator of neurotomy. This claim was disputed by
Moorcraft, who appears to have successfully shown himself to be the real person
entitled to that honour, he having satisfactorily performed the operation on numerous
animals for fully eighteen years prior to Professor Sewell’s announcement. It appears
that Moorcraft left this country for India in 1808, having practised the operation in
more or less obscurity for some six or seven years previous to that. After his
departure neurectomy, as introduced by him, either died away in repute, or was not
made by him sufficiently public to become a matter of general knowledge. To Professor
Sewell, therefore, although not the actual originator of the operation, belongs the
honour of making it public to the veterinary profession.

In 1824, five years after Sewell’s introduction, we find it practised on the
Continent by Girard. We gather, however, from the writings of Percival and Liautard,
that both in this country and on the Continent the operation was for several years
largely in the stage of experiment. Unsuitable subjects were operated on; the work
afterwards given to the animal improperly adjusted to his altered condition; and the
bad after-results of the operation almost ignored by some, and greatly exaggerated by
others. In fact, some long time elapsed before veterinary surgeons allotted to the
operation that measure of credit which the results following it warranted.

The Object of the Operation is to render the foot insensitive to pain, and
to give to an otherwise incurably lame animal a further period of usefulness. After
the operation, as time goes on, this object may become defeated by the reunion of the
divided ends of the nerve. In that case, neurectomy must necessarily be performed
again.

The Operation.—Two forms of neurectomy are recognised—the high
operation and the low. The low operation deals with the posterior digital branch of
the plantar nerve, and the high operation with the plantar itself.

It is the latter operation with which we shall deal first. In our opinion it is
that most likely to be followed by satisfactory results. The area supplied by the
posterior digital is mainly the posterior portion of the digit. Thus, unless the
cause of the lameness is diagnosed with certainty to be situated somewhere in the
posterior region of the foot, section of the posterior digital alone will not give
total insensibility to pain. Added to that, we may remember this: Below the point at
which the digitals branch off from the plantar there is always more likelihood of the
part we are attempting to render insensible being supplied by another and
adventitious branch, or a branch that, as regards its direction, is abnormally
distributed. As a last consideration, we may say that the higher operation is the
easier to perform.

Percival, in his works on lameness, has some very sage remarks to make by way of a
preliminary, and we cannot do better than quote them here. He says:

‘To command success in neurectomy three considerations demand attention:

‘1. The subject must be fit and proper; in particular, the disease for which
neurectomy is performed should be suitable in kind, seat, stage, etc.

‘2. The operation must be skilfully and effectually performed.

‘3. The use that is made of the patient afterwards should not exceed what his
altered condition appears to have fitted him for.

‘The veterinarian who is guided by considerations such as those will find that he
has restored to work horses who would otherwise have been utterly useless. A plain
and safe argument wherewith to meet the objections to neurectomy is simply to ask the
question what the animal is worth, or to what useful purpose he can be put, that
happens to be the subject of such an operation.

‘If the horse can be shown to be still serviceable and valuable, then he is not a
legitimate subject for the operation. The rule of procedure I have laid down is to
operate on no other but the incurably lame horse; and whenever this has been
attended to, not only has success been the more brilliant, but indemnification from
blame or reproach has been assured.’

Preparation of the Subject.—But little in the way of medicinal
preparation is necessary. When the animal is a gross, heavy feeder, and carries a
more than ordinary amount of cupboard, all that is needed is to withhold his usual
allowance of food for some time prior to the operation, simply to avoid risk of
rupture when casting. If considered advisable, a dose of physic may also be
administered.

To the seat of operation, however, careful attention should be given. On the day
previous to the operation the hair should be closely removed with the clipping
machines, and the skin thoroughly cleansed with warm water and soap. After this, a
bandage soaked in a 4 per cent, watery solution of carbolic acid should be wrapped
lightly round the limb, and allowed to remain in position until the animal is cast
and ready for the operation the following morning. On removing the bandage prior to
operating, the part should again be bathed with a cold 5 per cent. solution of
carbolic acid and swabbed dry. Attention to these details will serve to leave the
wound in that favourable condition in which it heals nicely, and with the minimum
amount of trouble.

Preliminary Steps.—By some practitioners the operation is performed
with the animal standing, local anæsthesia having been first obtained by the
use of cocaine, or an ethyl chloride spray. There is no gainsaying the fact, however,
that the operation of neurectomy is a painful one, and that, with most operators,
success will be more fully guaranteed with the animal cast and the limb held in a
suitable position by an assistant.

The animal is thrown by the hobbles upon the side of the leg which is to be
operated on. The cannon of the upper fore-limb is then fixed to the cannon of the
upper hind, as described under the section of this chapter devoted to the methods of
restraint, and the lower limb freed from the hobbles and drawn forward by an
assistant by means of a stout piece of cord round the pastern.

An alternative method of holding the limb is to bind both fore-legs together above
the knee by means of the side-line run round a few times in the form of the figure 8,
and then fastened off. As in the former method, the lower foot is then removed from
the hobble, and again held forward by an assistant. By either method the inside of
the limb is operated on first.

FIG. 57.—THE ESMARCH RUBBER BANDAGE AND TOURNIQUET.

Although it is not absolutely necessary, it is an advantage, especially to the
inexperienced operator, to apply before operating an Esmarch’s bandage and tourniquet
(Fig. 57). This expels the greater part of the blood from the limb, and renders the
operation comparatively bloodless.

FIG. 58.—RUBBER TOURNIQUET WITH WOODEN BLOCK. The Esmarch bandage is
composed of solid rubber, and with it the limb is bandaged tightly from below
upwards. On reaching the knee the tourniquet is stretched round the limb, fastened by
means of its buckle and strap, and the bandage removed. Those who feel they can
dispense with the bandage use the tourniquet alone. For this purpose the form
depicted in Fig. 58, and the one in general use at the Royal Veterinary College, is
more suitable, on account of its wooden block, which may be placed so as to press on
the main artery of supply.

Fig. 59. NEURECTOMY BISTOURY.

Instruments Required.—These should be at hand in an earthenware or
enamelled iron tray containing just sufficient of a 5 per cent. solution of carbolic
acid to keep them covered. Those that are necessary will be a sharp scalpel, or, if
preferred, one of the many forms of bistoury devised for the purpose (see Fig. 59), a
pair of artery forceps, a needle ready threaded with silk or gut, one of the patterns
of neurectomy needle (see Fig. 60), and a pair of blunt-pointed scissors curved on
the flat. It is also an advantage, when once the incision through the skin is made,
to employ one of the forms of elastic, self-adjusting tenacula (see Fig. 61) for
keeping the edges of the wound apart while searching for the nerve.

FIG. 60. NEURECTOMY NEEDLE.

Incision through the Skin.—We remember that the plantar nerve of the
inner side is in close relation with the internal metacarpal artery, and that both,
in company with the internal metacarpal vein, run down the limb in close proximity
with the inner border of the flexor tendons. Also, we remember that the external
plantar nerve has no attendant artery, although, like its fellow, it is to be found
in close touch with the edge of the flexor tendons.

Bearing these landmarks in mind, we feel for the nerve in the hollow just above
the fetlock-joint by noting the pulsations of the artery, and determining the edge of
the flexor tendons. This done, a clean incision is made with the bistoury or the
scalpel in the direction of the vessels. The incision should be made firmly and
decisively, so that the skin may be cleanly penetrated with one clear cut. If
judiciously made, little else in the shape of dissection will be needed.

FIG. 61.—DOUBLE TENACULUM.

It is now that the double tenaculum (Fig. 61) is applied. One clip is fixed to the
anterior edge of the wound, and the other carried beneath the limb and made to grasp
the posterior edge. If found desirable to keep the edges of the wound apart, and no
tenaculum to hand, the same end may be accomplished by means of a needle and silk. In
like manner as is the tenaculum, the silk is attached to one edge of the wound,
carried under the limb, and firmly secured to the other.

Having made the incision, the wound should be wiped free from blood by means of a
pledget of cotton-wool previously soaked in a carbolic acid solution and squeezed
dry. At the bottom of the wound will now be seen the glistening white sheath,
containing the vein, artery, and nerve. This should be picked up with the forceps,
and a further incision made with the bistoury. Care should be exercised in making
this second incision, or the artery may accidentally be opened. If an ordinary
scalpel is used, the lower end of the sheath should be picked up and the point of the
scalpel inserted through it. With the cutting edge of the scalpel turned towards the
opening of the wound, the sheath is then slit from below upwards. The second incision
satisfactorily made, the wound is again wiped dry, and the nerve seen as a piece of
white, curled string in the posterior portion of the wound.

At this stage it is advisable to accurately ascertain whether what we have taken
to be the nerve actually is it. This is done by taking it up with the forceps and
giving it a sharp tweeze. A sudden struggle on the part of the patient will then
leave no doubt in the operator’s mind that it is the nerve he has interfered
with.

Section of the Nerve.—The neurectomy needle (Fig. 60) is now taken,
and, excluding the other structures, passed under the nerve. A piece of stout silk or
ordinary string is then threaded through the eye of the needle, the needle withdrawn,
and the silk left in position under the nerve. The silk is now tied in a loop, and
the nerve by this means gently lifted from its bed. With the curved scissors or the
scalpel it is severed as high up as is possible. The lower end of the severed nerve
is then grasped firmly with the forceps, pulled downwards as far as possible, and
then cut off. At least an inch of the nerve should be excised.

The animal is then turned over, and the opposite side of the limb operated on in
the same manner.

The tourniquet is now removed, and the wound is examined for bleeding vessels. If
the hæmorrhage is only slight, the wound should be merely dabbed gently with
the antiseptic wool until it has stayed. A larger vessel may be taken up with the
artery forceps and ligatured, or the hæmorrhage stopped by torsion. On no
account, unless it it done to stay hæmorrhage that is otherwise uncontrollable,
should the wound be sutured with blood in it. With the wound once dry and clean, it
is well to insert three or four silk sutures, but care must be taken not to draw them
too tightly. This done, the patient may be allowed to get up.
After-treatment.—This is simple. Over each wound is placed a pledget of
antiseptic cotton-wool or tow, and the whole lightly covered with a bandage soaked in
an antiseptic solution. For the first night the animal should be tied up short to the
rack, and the following morning the bandages removed. A little boracic acid or
iodoform, or a mixture of the two combined with starch (starch and boracic acid equal
parts, iodoform 1 drachm to each ounce) should now be dusted over the wounds, the
antiseptic pledgets renewed, and the bandage readjusted over all.

At the end of three or four days the bandages may be dispensed with. All that is
necessary now is an occasional dusting with an antiseptic powder, and, as far as
possible, the restriction of movement. At the end of a week the sutures may be
removed, and the animal turned into a loose box or out to pasture.

E. MEDIAN NEURECTOMY.

As a palliative for lameness when confined to the foot, one would imagine that the
plantar operation would be all sufficient. There are operators, however, who state
that the results following section of the median nerve have been such as to cause
them to entirely abandon the lower operation in its favour. If only for that reason a
brief mention of the operation must be made here.

The operation was first performed in this country in October, 1895, the subject
being one of the out-patients at the Royal Veterinary College Free Clinique.

For five or six years following this date Professor Hobday performed the operation
some several hundred times, and was certainly instrumental in bringing the operation
into prominence. Though so recently introduced here, it appears to have been
practised for several years on the Continent, originating in Germany as early as
1867. In that country a first public account of it was published in 1885 by Professor
Peters of Berlin, while in France it was introduced by Pellerin in 1892. In this
operation a portion of the median nerve is excised on the inside of the elbow-joint
just below the internal condyle of the humerus. Here the nerve runs behind the
artery, then crosses it, and descends in a slightly forward direction behind the
ridge formed by the radius.

The position of the limb most suitable for the operation is exactly that we have
described as most convenient for the plantar excision. The animal is cast, preferably
anæsthetized, and the limb removed from the hobbles, and held as far forward as
is possible by an assistant with the side-line.

Professor Hobday’s description of the operation is as follows:

‘A bold incision is made through the skin and aponcurotic portion of the
pectoralis transversus and panniculus muscles, about 1 to 3 inches (depending on the
size of the horse) below the internal condyle of the humerus, and immediately behind
the ridge formed by the radius. This latter, and the nerve which can be felt passing
over the elbow-joint, form the chief landmarks. The hæmorrhage which ensues is
principally venous, and is easily controlled by the artery forceps. In some cases I
have found it of advantage to put on a tourniquet below the seat of operation, but
this is not always advisable, as it distends the radial artery. We now have exposed
to view the glistening white fascia of the arm, which must be incised cautiously for
about an inch. This will reveal the median nerve itself situated upon the red fibres
of the flexor metacarpi internus muscle. If not fortunate enough to have cut
immediately over the nerve, it can be readily felt with the finger between the belly
of the flexor muscle and the radius.'[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. ix.,
p. 181.]

The nerve exposed, the remainder of the operation is exactly as that described in
removing the portion of the nerve in the plantar operation. The wound is sutured and
suitably dressed, and a fair amount of exercise afterwards allowed the patient.

F. LENGTH OF REST AFTER NEURECTOMY.

This is placed by the majority of surgeons at about three weeks to a month. Within
that period no excessive exertion should be undergone by the patient. A certain
amount of quiet exercise, however, is beneficial, facilitating the healing of the
wounds, and accustoming the animal to the altered condition of his limb.

G. SEQUELÆ OF NEURECTOMY.

These we shall relate collectively, making no distinction between those following
excision of the plantar nerve and those succeeding section of the median. It must be
remembered by the surgeon, however, that the unfortunate sequelæ we are now
about to describe are likely to be far more grave when following section of the
larger nerve.

Liability of Pricked Foot going undetected.—On account of the warning
they convey to the surgeon, first place among the sequelæ of neurectomy must be
given to accidents following loss of sensation. Take, for example, punctured foot. In
any case, in the sense of being unforeseen, it is accidental. In the neurectomized
foot it becomes doubly accidental, in that not only is it unforeseen, but that it is
for some time indiscoverable. With the foot deprived of sensation, a nail may be
picked up, or a prick sustained at the forge, and no intimation given to the
attendant until pus has underrun the horn, and broken out at the coronet. What
follows, then, is that the hoof as a whole, or the greater part of it, sloughs
off.

No neurectomy should be undertaken unless this contingency has been allowed for.
The owner should be advised of it by the surgeon, who should at the same time enjoin
on his client the absolute necessity of giving to the neurectomized foot daily and
careful attention.

Loss of Tone in the Non-sensitive Area.—In addition to the mischief
resulting from a wound going undetected, it must be remembered that the loss of tone
resulting from the operation gives to every wound (however slight), in the region
supplied by the removed nerve, a sluggish and troublesome character. Difficult to
deal with as wounds about the foot ordinarily are, they are rendered more so by a
previous neurectomy.

Gelatinous Degeneration. This is a condition liable to occur in cases where
the operation has been too long deferred, and when considerable structural alteration
has already taken place in the shape of diseased bone or tendon, more especially in
navicular disease. It consists in a peculiar softening of the structures of the limb,
accompanied with enlargement, due to swelling of the connective tissues, the
enlargement and softening generally making itself first apparent by a soft, pulpy
swelling in the hollow of the heel.

From this onwards the enlargement increases, and lameness becomes excessive, the
animal going more and more on his heels, until, finally, no portion of the solar
surface of the foot comes to the ground at all.

The case is hopeless, and destruction should be advised.

Reported Case.—’The patient, a brown carriage gelding, was brought to
the Royal Veterinary College infirmary in a cart on December 31, the only previous
history obtainable being that it had suddenly fallen lame a month before.

‘The symptoms presented were excessive lameness of the near fore-limb. On being
trotted, the toe was elevated each time the foot reached the ground, progression
being entirely on the heels. Separation of the hoof for about 2 inches at the hinder
part of the coronet; oedematous swelling from foot to knee, extending during the next
three days to the elbow. Great tenderness between the knee and the fetlock; below
this no sensation whatever, as a pin was inserted in several places round the coronet
without causing any symptoms of pain. On further examination, two unnerving scars
were found. No treatment was adopted, and the horse was destroyed on January 6.

‘On dissecting the leg, the following appearances presented themselves:

‘The limb was very much enlarged, due to thickening of the connective tissue, the
skin being removed only with difficulty. The tendons were soft and much thickened. A
rupture of the skin at the coronet, just where the skin meets the wall of the foot.
Large extravasations of blood at the back of the tendons, situated in the lower half.
External nerve trunk had become reunited, at the point of junction there being
a hard lump about the size of a walnut. Internal nerve trunk also had become
reunited, and presented a thickened portion at the point of junction, but not so
large as that of the outer side, and situated in the lower half of the tendon, about
2 inches higher than that on the external nerve. This nerve trunk was atrophied below
the thickening, and had undergone gelatinous degeneration. Judging from the scars on
the skin, this side had evidently been unnerved a week or ten days previously to that
on the outer side. The band stretching across the back of the perforatus, between the
external and internal nerves, appeared on the inside to have become firmly fixed into
the tendon.

‘On removing the hoof, under the sole there appeared a large quantity of very
foetid pus; the laminæ were very much inflamed in patches. There was an
enormous thickening of connective tissues in the heel. On cutting longitudinally
through the perforatus tendon, there was exposed a large blood-coloured mass, of a
gelatinous appearance, situated on the perforatus tendon, the latter being very much
thickened, and growing to the navicular bone. The underneath surface of the superior
suspensory ligament was much thickened, and firmly adherent to the bone; at the
posterior surface of the metacarpus there was a quantity of gelatinous substance. The
anterior ligament of the fetlock-joint was thickened; the navicular bone was entire,
but showed lesions of navicular disease, being ulcerated. Section through the bone
did not reveal anything further. It may be here remarked that the ulcerations were on
either side of the central ridge, and not at all on the ridge itself.

‘Microscopic examination of the tissue joining the two ends of the nerve together
revealed a few nerve fibres; the general appearance was that of granulation tissue,
containing capillary vessels, which were fairly plentiful, and comparatively large in
size.'[A]

[Footnote A: Veterinary Record, vol. iv., p. 386 (Hobday)]

Chronic Oedema of the Leg.—In some cases there is a distinct swelling
of the leg some time after the operation. This exposes the limb to the infliction of
sores from striking with the opposite foot, with, of course, the difficulty in
healing we have just described.

Persistent Pruritus.—This annoying sequel occurs in the neurectomized
limb, with or without gelatinous degeneration, and appears to be without a remedy.
The itching in some cases is so intense as to lead the animal to constantly gnaw at
the top of the foot. As one observer has remarked, the animal may begin literally
biting pieces out of his limb. The result of the irritation and gnawing is fatal.
Great sloughing of the parts takes place, and the animal has eventually to be
slaughtered. vFracture of the Bones.—The sudden loss of sensation in a
foot may cause the animal to use violently the limb he has for months past been
carefully nursing. It may be that the lameness for which the operation has been
performed has been due to disease existing in the navicular bone, and extending,
perhaps, to the os pedis. By the disease the bone has already been made brittle, its
substance and ligamentous attachments perchance weakened and broken up by a
slow-spreading caries, and rarefaction of the remaining bone substance rendered
almost certain. In this instance, the free use of the foot, and the application to
the diseased structures of an unwonted pressure immediately after the operation
results in fracture. With the rupture of the structures we get the elevated toe and
soft swelling in the heel, as described in gelatinous degeneration. Treatment, of
course, is out of the question.

Neuroma.—A further sequel is the appearance at the seat of the
operation of what is termed an ‘amputational neuroma.’ This is a tumour-like growth
occurring on the end of the divided nerve. It is composed of connective-tissue
elements permeated by nerve fibres which have grown out from the axis-cylinders of
the nerve stump. It may vary in size from a pea to a hazel-nut, and is frequently the
cause of much pain. This must be cut down upon and cleanly removed, taking away at
the same time as much of the nerve as is possible.

Reunion of the Divided Nerve.—We may say at once that ‘reunion’ in
the popular sense of the word does not take place. At a varying period after section,
however, we do get a return of sensation. This is brought about in the following
manner: The axis-cylinder of the nerve, still in connection with the spinal cord,
swells somewhat, and hypertrophies. The cells of this hypertrophied portion show a
great tendency to proliferate and produce new nerve structure. This growing point
splits, and gives rise to several fibrils, which are new axis-cylinders. These
commence to grow towards the periphery, and, in so doing, grow through the
cicatricial tissue that has formed at the seat of the operation.

After passing through the cicatricial tissue (the amount of which tissue, of
course, controls the length of time that insensibility remains), the growing
axis-cylinders reach the degenerated portions of the nerve below the point of
section. It is along the track of the old nerve that the new growths from the stump
reproduce themselves.

The fact of the new growths having to pass through the fibrous tissue of the
cicatrix before they can gain the course of the old nerve, along which latter their
progress of growth is comparatively easy, affords ample illustration that as large a
portion as is possible of the nerve should be removed when operating, in order to
convey insensibility for the longest time. After reunion, of course, nothing remains
but to repeat the operation.

The Existence of an Adventitious Nerve-supply.—While not exactly a
sequel of the operation, the fact that it is not discovered until after the operation
has been performed warrants us in mentioning it here. It is not an uncommon thing in
the lower operation to find that sensation and symptoms of lameness still persist
after section of the nerve. In many cases this has been traced to the existence of an
abnormal nerve branch. In the higher operation this is not so likely to be met with.
That it may occur, however, is shown by the following interesting case related by
Harold Sessions, F.R.C.V.S.:[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. xii.,
p. 343.]

‘In June of 1898 I saw a hunter suffering from navicular disease. After carefully
examining the leg, I advised the owner to have the operation of neurectomy performed
upon him. This he decided to do, and the horse was sent to me about the beginning of
July.

FIG. 62.—DISSECTED EXTERNAL METACARPAL NERVE AND BRANCHES. a,
Metacarpal; b, anterior plantar; c, extra branch (probably from the
internal metacarpal), conveying sensation after division of the external
metacarpal.

‘The operation was performed in the ordinary way, without any difficulty whatever.
The wounds healed nicely, but the horse still continued to go lame. Careful
examination showed that there was still sensation on the outside of the foot.
Thinking that possibly there might be two external metacarpal nerves, the horse was
again cast, the operation being performed slightly lower down. Only the main branch
of the external metacarpal nerve could be found. A piece of this was taken out, and
the horse let up. On examination, sensation was still found in the posterior part of
the outside of the foot. It was very evident that there was some abnormal
distribution of the nerve, as sensation was still being conveyed to that part of the
foot.

‘As the horse was absolutely useless, and would have to be shot unless this piece
of nerve could be found, he was again thrown, and after he had been
anæsthetized I determined to follow the course of the nerve down, until I found
where the accessory branch came from. This I found a little below the fetlock, about
1/2 inch below the point where the anterior plantar nerve is given off from the
metacarpal nerve. It was about 1/2 inch below the spot where the anterior plantar
nerve passes between the artery and vein of the foot, and it was somewhat difficult
to get at it.

‘Fig. 62 shows the exact size and distribution of the nerves. After the separation
of the accessory branch, sensation was taken from the foot, and the horse went
perfectly sound.’

Stumbling.—In addition to the sequelæ we have mentioned, it is
urged against the operation of neurectomy that one of the first effects of depriving
the foot of the sense of touch is a tendency on the part of the animal to stumble.
From the cases we have seen we cannot regard this objection as a serious one.
Nevertheless, as veterinarians, with a knowledge of the physiology of the structures
with which we are dealing, we must treat the objection with respect, for, after all,
we are bound to allow that stumbling, and a bad form of it, would be but a natural
sequence of the operation we have just performed. The real fact remains, however,
that cases of stumbling, even immediately after the operation, are rare; and that
even when they do occur, the animal seems easily able to accommodate himself to the
altered condition, and as readily uses the comparatively inert mass at the end of his
limb as he did previously the intact foot.

H. ADVANTAGES OF THE OPERATION.

From the prominence we have given to the unfortunate sequelæ of the
operation it might possibly be inferred that, while not giving it our absolute
condemnation, we regard neurectomy with a certain amount of distrust. That we may
contradict any such false impression, we state here that in many cases the operation
is the only measure which will offer relief from pain, and restore to work an
otherwise useless animal. In support of that we will now quote the recognised
advantages of the operation.

That in many cases, when all other methods—surgical and medicinal—have
failed, there is an immediate and total freedom from pain and lameness no one will
deny. This, if it restores to active work an animal that would otherwise have had to
have been cast aside, is ample justification for giving the operation, in spite of
its many unfortunate terminations, a real place among the more highly favoured
remedial measures to our hand.

‘For Contracted Hoofs, viewing them in the light of idiopathic disease, or
as being the immediate cause of the existing lameness in the uninflamed condition of
the foot, and when consequential changes of its organism have taken place which bid
defiance to therapeutic measures, neurotomy is a warrantable resource‘
(Percival).

‘For Ringbone neurotomy has been practised with perfect success, after
blistering and firing had both failed, notwithstanding the work the animal had to
perform afterwards was of the most trying nature’ (ibid.).

For Navicular Disease, when that malady is diagnosed, the earlier
neurectomy is performed the better. The greater work given to the diseased bursa and
bone, and the return of the contracted heels to the normal, brought about by the
greater freedom with which the foot is used, are claimed by many to effect a
cure.

Writing of navicular disease, and mentioning his belief in the possibility of the
diseased bone effecting its own repair after the operation, Harold Leeney,
M.R.C.V.S., says:

‘The expansion of the heel, and rapid development of the frog (in this and many
other cases) immediately after the operation, has not, I venture to think, attracted
so much attention as it deserves, and may have something to do with those cases which
appear to be actually cured, not merely made to go sound by absence of
pain.'[A]

[Footnote A: Veterinary Record, vol. xi., p. 297.]

Speaking of the median operation before a meeting of the Central Veterinary
Medical Society, Professor Hobday says:[A]

[Footnote A: Veterinary Record, vol. xiii., p. 427.]

‘For old-standing lamenesses, when due to splints, exostoses, chronically
sprained, thickened, and painful perforans and perforatus tendons, or cases of that
kind which cause pain by pressing on the adjacent nerve structures, after all other
known methods have failed, median neurectomy is the operation which will be most
likely to give the animal a new lease of life and usefulness.’

‘Of the Humanity and Utility of Neurectomy there can be no question
whatever, and provided the cases are well selected, and the operation is efficiently
performed, the advantages to be derived from it are most striking as well as
enduring. But the disadvantages attending the loss of sensation in the foot have been
brought forward on many occasions as an argument against neurectomy, and no one can
deny that the foot with sensation is better than one without that faculty. But in a
long experience of the operation I have never found these disadvantages outweigh the
great advantages which have immediately followed it.'[A]

[Footnote A: Veterinary Journal, vol. ix., p. 178 (Fleming).]

Beyond these, the direct advantages of neurectomy, are other and more indirect
advantages which claim attention.

The most astonishing among them is the fact noted by many writers of repute that
exostoses (ringbones, side-bones, splints, etc.) rapidly diminish in size. This is
vouched for by such well-known authorities as Zundel and Nocard.

Percival, too, mentions at some length the effect of the removal of pain on the
oestral and generative functions, quoting a case of a brood cart-mare by reason of
bony deposits being stayed from breeding for some years. Two months after the
operation she went to work, and moved sound, her altered condition leading her to
breed several healthy foals.

I. THE USE OF THE HORSE THAT HAS UNDERGONE NEURECTOMY.

No operation is of any considerable value to the veterinary surgeon unless he is
able to show that after it he has left his patient workable. The alleviation of pain
alone, commendable as it is from a humanitarian standpoint, is of no interest to the
average owner of horse-flesh, unless with it he sees his animal capable of justifying
his existence by the amount of labour performed.

Criticised in this way, is the operation of neurectomy justifiable? Upon that
point the opinions of many practitioners, even at the present day, differ. We have
already partly answered the objections likely to be raised on this score by stating
that the work afterwards allotted the animal should be fixed to suit his altered
condition. It may be taken as a general rule that in all cases where the animal’s
usefulness depends upon his delicacy of touch, as, for example, animals used solely
for hacking or hunting, his future usefulness in that special sphere of work will be
done away with.

Percival himself, always a strong advocate for the operation, fully recognises
this. ‘Does the neurotomized horse maintain the same step as before?’ he asks. ‘To
this important question,’ he replies, ‘I unhesitatingly answer no; he does not. There
can be no doubt but that the horse feels the ground upon which he is treading,
and that he regulates his action in consonance with such feeling, so as to render his
step the least jarring and fatiguing to himself, and therefore the easiest and
pleasantest to his rider…. Such impressions’—those of touch—’being in
the neurotomized subject, so far as regards the feeling of the foot, altogether
wanting, a bold, fearless projection of the limb in action will be the consequence,
followed by a putting down of the hoof flat upon the ground, as though it were a
block, creating a sensation alike unpleasant both to horse and rider.’

Emphatic as Percival is upon this point, there are, nevertheless, others who
maintain with equal stoutness that the unnerved animal is positively as safe, if not
safer, than the animal who has not been so treated.

‘That the tactile sense in the horse’s foot is useful, it would be idle to deny;
but that it is absolutely essential, even to safe progression, no one who has paid
attention to the results of plantar neurectomy will maintain. On several occasions
for years I have hunted, hacked, and driven horses which have been deprived of
sensation in their fore-feet, and never had an accident with them. Their action has
not been impaired by the operation; on the contrary, it has been vastly improved
compared with what it had been previous to it. And my opinion has not been single in
this respect, as many competent horsemen can give like evidence after long and severe
trials of neurotomized horses. The opponents of neurotomy were, probably, not aware
that there is in progression a muscular as well as a tactile
sense.’

This latter contention is supported by numerous cases, reported at the time when
the operation of neurectomy was at the heyday of its popularity. Two I select from
writings of a later period:

Recorded Cases.—1. ‘Two of the finest among the many fine horses in
the Second Life Guards were so lame from navicular disease, when I joined the
regiment, that they were unsafe and unsightly to ride, and were therefore entered on
the list to be cast off and sold. One was so crippled that it could scarcely be moved
out of its stable. Peeling sorry at having to get rid of such good horses, and
anxious to give another blow to the mistaken theory that unnerved animals were
unsafe, I obtained the consent of my commanding officer, who patronizes practical
conclusions, to perform neurotomy. This was carried out on both horses about eighteen
months ago. Within a fortnight they were at their duty, absolutely free from
lameness, and with first-rate action, and one of them, from being troublesome and
unsteady in the ranks—probably from the pain in its feet—had become quite
steady and tractable. Instead of being lame, blundering, and unsafe, both were sound,
free in movement, and secure, and, the pain being abolished, they looked improved in
condition.

‘During the month of July the regiment attended the summer drills at Aldershot,
and five days every week for a month these horses carried a weight of about 22 stones
each over the roughest and most dangerous ground, nearly always at a fast pace, and
for four, five, or six hours each day; and yet they never fell or blundered, and the
troopers who rode them had unbounded confidence in their sure-footedness. They
returned to Windsor, at the end of the month’s severe test, as sound in their paces
as when they left, and certainly now offer no indication whatever that they are less
safe to ride than any other horse in the regiment. The effects of the relief from
pain are also most marked, not only in the altered gait out of doors, but also in the
stable.'[A]

[Footnote A: Veterinary Journal, vol. ix., p. 178 (George Fleming,
F.B.C.V.S.).]

2. ‘Some years ago I operated upon a valuable hunter, the property of a gentleman
in Kildare, the animal having shown unmistakable symptoms of navicular disease for
some months previously, and which had been unsuccessfully combated by the milder
forms of treatment for the disease without any benefit. Although the horse went
sound, the owner feared to ride him, and sent him to be sold in Dublin, where he was
disposed of for a small price, and I then lost sight of him. The following
Punchestown Races, to my surprise, amongst a group of horses walking round the
paddock previous to saddling for an important race, I recognised my old patient,
bandaged, clothed, and trained, ready to take his part in the cross-country contest,
and surrounded by a host of admirers willing to back him at any price.

‘Having satisfied myself that it was no other than the same animal, my first
impulse was at once to find out the jockey who was to ride him, and warn him of his
danger by telling him his mount was devoid of feeling in both fore-feet; but the
saddling-bell had already rung, and in a few moments more the jockey emerged from the
weighing-room and the next view of the horse was his tearing up the course in the
preliminary, and “pulling double.” I was sorry for the jockey if he felt as I did at
that moment, for if he did I fear he and his horse would have parted company at the
first fence, as I was certain there would be a smash before the end of the long and
difficult three miles of the Kildare Hunt Cup course. It was not until I saw him
again in the front rank passing the stand, in the first round, that I breathed
freely, and even then I felt very guilty, and, had he come to grief badly, I don’t
think I should ever have operated on another horse except in such a way as would have
left unmistakable traces after it.

‘”The old horse wins!” screamed a thousand voices as the competitors safely
cleared the last bank (now taken away for a gorse fence) the last time round, and
from that moment the operation went up in my estimation a hundredfold, and I almost
lost all interest in the finish (and it was a close one, with my patient a good
third), resolving I would operate for the future on every animal, young and old,
which showed symptoms of navicular disease.

‘Neither owner nor jockey knew the horse had been operated on, and he was soon
after, on the strength of his performance, sold for a good price to come to England.
It is idle to think that all cases are as successful as this was, as experience soon
told me; but I consider that, in careful hands, the advantages well outweigh the
disadvantages of the operation, and I have selected this instance merely as a
practical example.'[A]

[Footnote A: Veterinary Journal, vol. iii., p. 254 (W. Pallin,
M.B.C.V.S.).]

It is solely with the object of ventilating both sides of the question that we
quote the last two cases. In our opinion, the colours in which the results of the
operation are there painted are far too rosy. The practitioner who has before him the
task of satisfying a client as to what will or what will not be the results of an
operation he has suggested will do well to weigh each side of the argument carefully,
and endeavour in his explanation to strike the happy mean.

We hold, further, that the animal who has previously been accustomed to fast work,
and to work entailing a large call upon the sense of touch when passing over rough
and uneven ground, will be far more likely, in his neurectomized condition, to give
satisfaction to his owner if put to a slower and a more suitable means of earning his
living.

CHAPTER VI

FAULTY CONFORMATION

Under this heading we shall deal with such formations of the feet as depart
sufficiently from the normal to render them serious. Faulty conformation may be
either congenital or acquired, and acquired gradually as the result of slowly
operating causes, or suddenly as the sequel to previous acute disease. Whether
congenital or acquired, serious in its nature or comparatively of no account, the
veterinary surgeon will often find that the matter of conformation is one which will
have a direct bearing on many of his ‘foot’ cases, and, furthermore, that it is one
upon which he will often be called to give advice.

A. WEAK HEELS.

Definition.—That condition of the wall in which, owing to the
softness of the horn and the oblique direction of the horn fibres, the heels are
unable properly to bear the body-weight, and, as a consequence, curve in beneath the
sole. We give the condition first mention, not because of its greater importance, but
for the reason that it is frequently the forerunner of the condition to be next
described—namely, contracted feet.

Symptoms.—The extreme point of the heel is not affected unless the
foot has been greatly neglected, and the condition allowed to develop. Where,
however, the foot has been uncared for, curving in of the wall takes place to an
alarming degree, and the heels curl underneath the foot to such an extent as to grow
over the sole and the bars. By the pressure they exert on the sole corns result, and
the animal is lamed.

Causes.—In the main this defect is hereditary. It is seen commonly in
connection with flat-foot, and where the horn of the wall is thin and shelly.

Treatment.—In the case of weak or ‘turned in’ heels no suitable
bearing is offered for the shoe in the posterior half of the foot. Any attempt to
induce the heels to bear weight is immediately followed by their bending in. It
follows from this that the best shoe to be used here is one in which the bearing is
confined to the anterior half of the wall, the heels being relieved by being
sufficiently pared. As might be expected, this bearing on the anterior half only of
the foot is insufficient; pressure must be given the frog. This latter end is best
gained by a bar shoe (Fig. 68). With it the anterior portions of the wall, the whole
of the bars, and the whole of the frog may be in contact, and the heels only so pared
as to take no bearing at all. A few such shoeings sees the defect remedied. In every
instance paring of the sole should be discouraged, as it serves but to increase the
deformity.

B. CONTRACTED FOOT.

(a) GENERAL CONTRACTION—CONTRACTED HEELS.

Definition. By the term contracted foot, otherwise known as hoof-bound, is
indicated a condition in which the foot, more especially the posterior half of it,
is, or becomes, narrower from side to side than is normal.

It must be borne in mind, however, that certain breeds of horses have normally a
foot which nearer approaches the oval than the circular in form, and that a narrow
foot is not necessarily a contracted foot.

The contraction may be bilateral when affecting both heels of the same foot and
extending to the quarters, or unilateral when the inside or outside heel only is
affected.

In some cases contraction is confined to one foot, while in others it may be
noticed equally bad in both. It is a matter of common knowledge that contraction is
usually seen in the fore-feet, while the hind seldom or never suffer from it, a fact
which, to our minds, seems difficult of adequate explanation. Zundel explains this by
stating that contraction is principally observed in the fore-feet, by reason
of the fact that when lameness arises from it alteration in action will more readily
be detected in front than behind. Percival, on the other hand, suggests that the
greater expansive powers of the hind-foot, by reason of the impetus of its action, is
able to overcome any influence operating towards contraction. It may be, however,
that given a cause for contraction, such as the removal of the frog’s
counter-pressure with the ground by faulty shoeing or excessive paring, the
fore-feet, by reason of their being called upon to bear the greater part of the
body-weight, are the first to suffer.

Flat feet with weak heels are those most frequently affected, and, as we have
already intimated, the condition may exist with or without other disease of the
foot.

Depending upon its degree, contracted foot may vary from a simple abnormality,
non-inflammatory and painless, to a condition in which it becomes a veritable
disease, giving rise to a bad form of lameness, and bringing about a withered and
sometimes discharging and cankerous affection of the frog.

Symptoms.—In its early stages contraction is difficult of detection,
and where both feet are affected may for some time go unsuspected. With only one foot
undergoing change, the early stages may the more readily be marked, for in this case
comparison with the other and sound foot will at once reveal the alteration in shape.
If lameness in the suspected foot is present, then any lingering doubt will be
quickly dispelled.

When far advanced, contraction offers signs that cannot well be missed. The
converging of the heels narrows the V-shaped indentation in the sole for the
reception of the frog. As a consequence of this, the frog itself becomes atrophied by
reason of the continual pressure exerted upon it by the ingrowing horn of the
wall and the bars. The median and lateral lacunæ of this organ, from being
fairly broad and open channels, become pressed into mere crack-like openings (see the
commencing of this condition in Fig. 80, and a badly wasted frog in Fig. 74A). As the
case goes on, the lateral branches of the frog entirely disappear, and all that is
left of the organ is a remnant of its body or cushion, now wedged in tightly between
the bars. Following upon the disappearance of the frog, we find that the bars are in
contact, or, in some cases, actually overlapping each other at their posterior
extremities.

At this stage, perhaps, the whole condition has become aggravated by a foul
discharge from the place originally occupied by the frog, and the foot, especially in
the region of the heels, has become hot and tender—really a form of local and
subacute laminitis.

The long-continued inflammation, although only of a low type, renders the horn of
the hoof hard and dry, and only with difficulty will the ordinary foot instruments
cut it. This in its turn leads to cracks and fissures in various places, but more
especially in the bars and what is left of the frog. Often, too, cracks will appear
in the horn of the quarters, and a troublesome and incurable form of sand-crack
results.

An animal with contraction advanced as far as this, especially if confined to one
foot, goes unmistakably lame. With both feet affected, he ordinarily starts out from
the stable in a manner that is commonly called ‘groggy.’ In other words, the gait is
uncertain, and feeling; and stumbling is frequent. Anyone who has had the misfortune
to drive an animal with feet in this condition knows full well that every little
irregularity in the road at once makes itself felt to the feet, and that the animal,
as time goes on, learns to carefully avoid any suspicious-looking group of stones he
may see. To drive an animal like this is to keep one’s self continually on
tenter-hooks, for, sooner or later, the inevitable happens, and the animal comes
down.

Up to now we have described the changes of form in the hoof as seen when the
contracted foot is viewed from the solar surface. With those changes as evident as we
have depicted them, there will be no difficulty in detecting the alterations in the
form of the wall.

In addition to a narrowing from side to side there will be noticed an abnormal
straightness of the quarters, with a turning in, more or less sudden, of the heels.
This effect is given in these cases by the smith maintaining the shoe of a length and
width that should normally fit a foot of that particular animal’s size and substance.
This is probably done with the idea of deceiving anyone examining the solar surface.
Viewed from this position, the width of the shoe at the heels gives the impression
that it is attached to a foot of normal breadth. This deception is heightened if at
the same time has been practised the process of ‘opening up the heels.’ That
expression indicates that the bars have been removed, and the lateral lacunæ of
the frog made to continue the concavity of the sole. The arch of the latter is thus
made to appear of much greater extent than it really is, and the heels, by reason of
their being abruptly cut off when removing the bars, also convey the false impression
of being wide apart.

The practitioner unversed in the tricks of the forge will best guard against this
by viewing the foot, while on the ground, from behind. From that position he will be
able to detect the lowness of the quarters, and the projecting portion of the shoe,
that the hoof, by reason of its sudden bending inwards, does not touch.

The ‘feeling’ manner of the gait before alluded to, together with the
disinclination to put the foot firmly and squarely forward, will sometimes lead the
examiner to over-look the contraction, and diagnose his case as one of shoulder
lameness. In many cases, too, such consequent conditions as ‘thrushy frogs’ and
‘suppurating corns’ are often treated with utter disregard of the contraction that
has really brought them about. But above all, the disease most likely to be
confounded with simple contraction is navicular disease. More than probable it is
that many cases of so-called ‘navicular’ have in reality been nothing more than
contraction brought about by one or other of the causes we shall afterwards
enumerate—cases where a due attention to the prime cause of the mischief would,
in all likelihood, have remedied the lameness.

Changes in the Internal Structures.—It follows as a matter of course
that the changes we have described in the form of the hoof itself carry with them
alterations in the bones and sensitive structures beneath it. The tissues, as a
whole, become atrophied. The os pedis becomes deformed, loses its circular shape, and
gradually becomes more or less oval in contour. At the same time, its structure
becomes more compact, the cribriform appearance of its anterior and lateral faces
more or less destroyed, and the few remaining openings apparently increased in size.
This atrophy of the os pedis is best noted at the wings.

In the plantar cushion the effects of the atrophy are noted in the smallness of
the organ, in its becoming whiter in colour than normal, and more resistant to
pressure.

The coronary cushion is also affected in the same way, where the changes are noted
most in its posterior portions.

A further effect of the narrowing of the heels, and their consequent tendency to
drop downwards, is the exertion of a continual pressure on the sensitive sole. In
course of time, and especially in flat feet, this leads to the appearance of
corns.

The navicular bone and bursa and the tendon of the perforans also suffer from the
effects of compression. The movement of the tendon is restricted, and arterial supply
to the adjacent structures rendered deficient. The tissues of the bone and bursa are
insufficiently nourished, and the secretion of synovia lessened. In this way it is
conceivable that navicular disease may follow the condition of simple contracted
heels.

In common with the other structures, the lateral cartilages also suffer from the
continual pressure. Their blood-supply is lessened, their functions interfered with,
and side-bones result.

Causes.—Upon the causation of contraction a very great deal has been
written, both by early veterinarians and by those of the present day. Many and widely
differing opinions have been advanced, but a careful résumé of only a
few will lead one to certain fixed conclusions.

We may consider the causes of contraction under two headings—predisposing
and exciting.

Predisposing Causes of Contraction.—Among these we will first mention
heredity, although it is possible it should not be deemed of so great account as it
is by some. That the shape of certain feet, especially those with low heels and
abnormally sloping walls, predisposes to contraction no one will deny. So long,
however, as the animal goes unshod, so long does the foot maintain a normal condition
of the heels. In other words, it is not until the tendency to contraction already
there is aggravated by careless shoeing and the effects of work that it operates to
any noticeable extent.

The degree of contraction will also be very largely governed by the amount of the
development of the frog. With a frog of good size, low down, and taking part in the
pressure of the foot on the ground, contraction will be prevented. On the other hand,
an ill-developed frog, one wasted by long-continued and spreading thrush, or one
robbed of its normal function by excessive paring in the forge, is a common
starting-point of the condition we are considering. We have already referred to this
in Chapter III., when considering the experiments of Lungwitz in this connection.
What we have to bear in mind in these experiments is that the application of a pad to
the frog, in such a manner that effective ground-pressure is obtained, results always
in a marked expansion of the heels, and that, with counter-pressure with the ground
absent, expansion occurs to little or no extent. This is proof positive of the
enormous part the frog plays in maintaining an open and elastic condition of the
heels—a fact so insisted on by Coleman.

It is worthy of mention, however, that loss of the frog’s function does not
operate to nearly so serious an extent in horses with high, upright heels as in those
with the heels low and excessively sloping.

In illustrating this, Mr. Dollar, in his work on shoeing, mentions the case of a
pair of trotting horses of similar age, size, and weight, each having weak
fore-heels. In one case the hoofs were flat, in the other upright. The horse with the
flat hoofs suffered from contraction, while the other did not.

The reason appears to be that in the animal with upright hoofs the proportion of
body-weight borne by the heels is considerably less than in those with the hoofs flat
and sloping.

Certain conditions of the horn-producing membranes also predispose to contraction.
For example, in horses reared on marshy soils, and afterwards transferred to standing
in town stables, we find that a dry and brittle condition of the horn supervenes.
This we may regard as a low form of laminitis, brought about by the heat of the
material upon which the animal is standing, and the congestion of the feet engendered
by his enforced standing for long periods in one position, as opposed to the more or
less continuous exercise when at pasture. With the hoof in this condition it loses by
evaporation the moisture that normally it should contain, and, as we might expect, a
certain degree of contraction of its structure is the inevitable result.

We thus see that contraction brought about in this way is not so much caused by
the heat of the stable, as it is by the decreased ability of the horn to retain its
own moisture.

On the other hand, it cannot be denied that excessive warmth and dryness combined
tend also to an undue abstraction of moisture, even from the horn of the healthy
foot; and this explains in great measure how it is that lameness, as a rule, and
especially that proceeding from contracted heels, is far more frequent and of greater
intensity in the hot, dry months of summer, than in the cooler and more humid
atmosphere of winter. It is interesting to note, too, that an alternation of humidity
and dryness is far more liable to injure the quality of the horn and tend to its
contraction than the long-continued effects of dryness alone. A common illustration
of this is to be found in the effects of the ordinary poultice. Everyone knows that
when, after a few days’ application, they are discontinued, we get as a result an
abnormally dry and brittle state of the horn. This is doubtless due to the poultice
removing the thin, varnish-like, and protective pellicle known as the periople, and
thereby allowing the process of evaporation to act on the water normally contained in
the hoof.

Exciting Causes of Contraction.—Among these, first place must
undoubtedly be given to shoeing. This does not necessarily imply shoeing more than
ordinarily faulty, nor a faulty preparation of the foot, but shoeing as it is
generally practised. No ordinary shoe, except a few devised for the purpose, such as
the Charlier or the tip, allows the frog to come in contact with the ground. This we
take to be the main factor in the causation of contracted heels, especially with a
predisposition already present in the foot itself. In the words of Lungwitz:
‘Regarded from this point of view, there is no greater evil than shoeing. It
abolishes the necessary counter-pressure, and thus interferes with expansion. Bars,
sole, and frog cannot perform the functions that naturally belong to them as they
would do without the shoe.’

In addition to the evil of the shoe itself, errors of practice in the forge
contribute to the causation of contraction. Taking first the preparation of the foot,
we find that often the heels are lowered far too much, and the toe allowed to remain
too long. This can have but one effect—that of throwing a greater proportion of
the animal’s weight upon the heels than properly they should bear, with, what we now
know to be the consequence of that, a corresponding pushing inwards and downwards of
the horn; in other words, contraction.

Excessive paring of the bars, to which we have already partly alluded, is also an
active agent in bringing about an inward growth of the horn of the heels and
quarters. The bar, or inflexion of the wall at the heel, by means of its close
contact with the frog, communicates the outward movements of that organ to the wall
of the hoof. With the bar removed, the outward movements of the frog under pressure
are naturally rendered of no account, and a proper and intermittent expansion of the
wall denied it. The same evil follows, though to a less extent, excessive paring of
the sole.

The shape of the bearing surface of the shoe is often to be blamed. Where this is
concave—’seated’—and the ‘seating’ is carried back to the heels, it is
easy to see that, when weight is on the foot, there is an ever-present tendency for
the bearing edge of the wall to slide down towards the inner edge of the shoe. This
tendency, operating on both the inner and outer wall simultaneously, must strongly
favour contraction.

A further wrong practice is that of continuing the nailing too far towards the
heels. In our opinion this is not now often met with. When it occurs its effect is,
of course, to prevent those movements of expansion of the wall which we now know to
be normal and most marked at the heels.

It may be remarked of the build of the shoe, or of errors in the preparation of
the foot, that neither are of much moment. Neither are they. But when one stays to
consider that errors of this description are practised not only once, but each time
the horse goes to the forge, and that with some of them—those relating to the
build of the shoe—the injury thereby brought about is inflicted not only once,
but every day that particular shoe is worn, then it is not to be wondered at that,
sooner or later, ill consequences more or less grave result.

Prognosis.—This will depend to a very large extent upon the
conformation of the limb, and upon the previous duration of the contraction.
Contraction of long standing, where atrophy of the sub-lying, soft structures and the
pedal bone may be expected, will prove obstinate to treatment. Especially will this
be so if the lateral cartilages have become ossified. Neither may we look for much
benefit from treatment if the contraction has occurred in animals with an oblique
foot axis and flat hoofs.

On the other hand, if the case is comparatively recent, if the limb is straight
and the form of the hoof is upright, and if matters are uncomplicated by side-bones,
or other serious alteration in the internal structures, then treatment may be
rewarded with some measure of success.

FIG. 63.—TIP SHOE. The dotted portions represent the length of the branches
removed.

Treatment.—The greater part of the treatment of contracted foot will
almost suggest itself as a corollary of the causes we have enumerated. The normal
width of the heels may be renewed, and development of the wasted frog brought about
by one of three methods:

1. By restoring the pressure from below to the frog.

2. By the use of an expansion shoe.

3. By operative measures upon the horn of the wall.

1. By Restoring the Pressure from Below to the Frog.

This may be accomplished as follows:

(a) By Shoeing with Tips.—This method is advocated by Percival, by
A.A. Holcombe, D.V.S., Inspector. Bureau of Animal Industry, U.S.A., by Dollar in his
work on horseshoeing, and by many others.

Though requiring more care than in fitting the ordinary shoe, the application of a
tip is simple. In reality, the tip is just an ordinary shoe shortened by truncating
the heels.

Before applying the tip, the horn of the wall at the toe should be shortened
sufficiently to prevent any undue obliquity of the hoof, and the foot should be so
prepared as to allow the heels of the tip to sink flush with the bearing edge of the
wall behind it.

When the foot does not allow of the removal of much horn at the toe, what is
termed a ‘thinned’ tip is to be preferred. Its shape is sufficiently shown by the
accompanying figure (Fig. 65).

With the tip the posterior half of the foot is allowed to come into contact with
the ground, and the object we are striving for—namely, frog pressure, and
greater facilities for alternate expansion and contraction of the heels—is thus
brought about.

FIG. 64.—THE TIP SHOE LET IN THE FOOT.

FIG. 65.—THE THINNED TIP.

(b) By Shoeing with the Charlier.—The results brought about by the
use of a tip may be arrived at by the application of a Charlier or preplantar shoe,
or by a modified Charlier or Charlier tip.

Briefly described, a Charlier is a shoe that allows the sole and the frog to come
to the ground exactly as in the unshod foot. This is accomplished by running a groove
round the inferior edge of the hoof by removing a portion of the bearing edge of the
wall with a specially devised drawing-knife. Into this groove is fitted a narrow and
somewhat deep shoe, made, preferably, of a mixture of iron and steel, and forged in
such a manner that its front or outer surface follows the outer slope of the
wall.

The Charlier should have the inner edge of its upper surface very slightly
bevelled, in order to prevent any pressure on the sensitive sole, and should be
provided with from four to six nail-holes. These latter should be small in size and
conical in shape. The nails themselves should be small, and have a conical head and
neck, to fit into the nail-hole of the shoe.

FIG. 66.—THE SPECIAL DRAWING-KNIFE (FLEMING’S) FOR PREPARING THE FOOT FOR
THE CHARLIER SHOE.

The modified Charlier, or Charlier tip, perhaps the better of the two for the
purpose we are describing, is really a shortened Charlier, and bears the same
relation to the Charlier proper as the tip does to the ordinary shoe. It is let into
the solar surface of the foot in exactly the same manner as its larger fellow, but it
does not extend backwards beyond the commencement of the quarters. By its use greater
opportunity for expansion is given to the heels than is done by the Charlier with
heels of full length.

FIG. 67.—FOOT PREPARED FOR THE CHARLIER SHOE.

We do not here intend to deal at any length with the arguments for and against the
Charlier as regards its adoption for general use. These will be found fully set out
in any good work on shoeing.

The point that it is correct in theory it would be idle to attempt to evade; but
that it is generally practicable, or that it offers any very pronounced advantages,
as compared with the disadvantages urged against it, over the shoes in ordinary use,
the limited favour it has drawn to itself, since its introduction in 1865, seems
sufficiently to deny.

(c) By the Use of a Bar Shoe.—Where the frog is not excessively
wasted benefit will be derived from the use of a bar shoe.

FIG. 68.—BAR SHOE.

The transverse portion at the back, termed the ‘bar,’ and which gives the shoe its
name, is instrumental in bringing about from below that counter-pressure on the frog
that we now know to be so necessary a factor in remedying contraction. When the frog,
by wasting or disease, is so deficient as to be unable to reach the ‘bar,’ this shoe
must be supplemented by a leather or rubber sole.

In the event of corn or sand-crack existing with the contraction, the shoe known
as a ‘three-quarter bar’ is preferable (see Fig. 103). The break here made in the
contour of the shoe allows of dressing the corn, and, in the case of sand-crack,
removes the bearing from that portion of the wall. (d) By the Use of a Bar Pad and
a Heelless or ‘Half’ Shoe.—The bar pad consists of a shape of rubber
composition firmly fixed to a leather foundation, which shape of rubber takes the
place of the ‘bar’ of the bar shoe.

FIG. 69.—RUBBER BAR PAD ON LEATHER.

FIG. 70.—THE BAR, PAD APPLIED WITH A HALF-SHOE.

For habitual use in such cases as prove obstinate to treatment, or where a
complete cure was never from the commencement expected, the bar pad is undoubtedly
one of the most useful inventions to our hand. The animal’s ‘going’ is improved, the
tender frog is protected from injury by loose stones, and greater comfort given to
both the horse and the driver.

FIG. 71.—FROG PAD.

FIG. 72.—FROG PAD APPLIED.

(e) By the Use of a Frog Pad and a Shoe of Ordinary Shape.—The shape
of rubber on this pad is designed to cover the frog only. Its shape and mode of
application is sufficiently shown in the accompanying illustrations.

(f) By turning out to Grass.—Where the expense of keep is no object,
a return of contracted feet to the normal may be brought about by removing the shoes
and turning the animal out to pasture, thus giving the feet the advantages to be
derived from a more or less continuous operation of the normal movements of expansion
and contraction. In this case the treatment must extend from three to four, or
possibly six months.

2. By the Use of Some Form of Expansion Shoe.

FIG. 73.—SMITH’S EXPANSION SHOE SEEN FROM ITS GROUND SURFACE AND FROM THE
SIDE. a, The screw, with a fine-cut thread; b, nut which travels along
it; c, a hollow thimble into which the screw passes at one end, the other
being cut out V-shaped to catch into a slot (d) on the shoe; e, e, the
grip[A] for the bars, the length and direction of which depend upon the shape of the
foot; f, f, the counter-sunk rivets forming the hinge (f‘); g,
the counter-sunk rivet of the expanding piece.

[Footnote A: The inventor of this shoe uses the word ‘grip’ to denote what, in
describing other expansion shoes, we term the ‘clip’ (H.C.R.).]

(a) Smith’s.—For many years past continental writers have been
practising this method. So far as we know, however, Lieutenant-Colonel Fred Smith was
the first English veterinarian to use a shoe of his own devising, and to report on
its effects. This shoe we will, therefore, give first mention.

The above figure, with its accompanying letterpress, sufficiently explains the
nature of the shoe. In fitting the shoe, care must be taken to have the hinges (f,
f) far enough back, or the shoe will have a tendency to spring at the heels, and
the grips (e, e), which catch on the bars, will have a difficulty in biting.
This trouble will be avoided by having the hinges about 1-1/2 to 2 inches from the
heels.

After the shoe has been firmly nailed to the foot, the travelling nut b is
driven forward on the screw a so as to cause the grips to just catch on the
inside of the bars of the foot. According to the inventor, the amount of pressure to
be exerted must be learned by experience, and he says:

‘I screw up very gradually until I see the cleft of the frog just beginning to
open. I now trot the horse up, and if he goes sound it is certain that the pressure I
have exercised will not give rise to trouble. The animal is sent to work to assist in
the expansion of the foot. On examining the shoe next day, the grip is found to be
quite loose, the foot has enlarged, and the nut is turned once more until the grip on
the bars is tightened, the horse being again trotted to ascertain that no injurious
pressure is exerted.

‘Every day or two I repeat this process, making measurements in all cases before
widening the heels. The increase in width of the foot which results is astonishing,
1/4 to 3/8 inch during the first week may be safely predicted, and in a month to six
weeks it is impossible to recognise in the large healthy frog and wide heels, the
shrivelled-up organ of a short time before.'[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. v., p.
98.]

It is pointed out by the writer of the above (and his observations, doubtless,
apply to the use of all other expansion shoes in which the bars are gripped and
forcibly expanded) that the whole secret of success lies in avoiding injurious
pressure by exerting too great an expansion at one operation. After each manipulation
of the expanding apparatus the horse should trot sound and the frog remain cool.
Should the foot become hot, and lameness supervene, then tension should at once be
relaxed.

Recorded Cases of the Use of the Shoe.—The inventor of the shoe
relates two cases of contracted foot treated by these means in which the heels of
one, after thirty-nine days’ treatment, had increased in width to the extent of 1
inch, and the heels of the other, after twenty-four days’, had enlarged 5/8 inch. Of
the first case he gives the drawings in Fig. 74.

A represents the foot before treatment; B the same foot after nine days’
treatment, when the heels had widened 3/4 inch; and C the same foot at the end of the
thirty-nine days’ treatment, at which date the frog was an excellent-looking one, and
the foot had increased an inch in width.[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. v., p.
100]

FIG. 74.—THE CHANGES IN FORM OF A CONTRACTED FOOT TREATED WITH SMITH’S
EXPANSION SHOE

In 1893, at a meeting of the Midland Counties Veterinary Medical Association, the
late Mr. Olver said he had applied this shoe to a valuable hunter that had gone so
lame that he could scarcely put his foot to the ground. After a fortnight’s
application, and by the assistance of the double screw in the shoe, the heel was
forced out. Then the horse was put to work with the shoe on, and he had hunted the
whole of the last season in a perfectly sound condition.[A]

[Footnote A: Veterinary Record, vol. vi., p. 143]

F.D. McLaren, M.R.C.V.S., writes:[A] ‘I resolved to try one of Captain Smith’s
shoes in a case where the hoof was badly contracted, and where the frog had entirely
disappeared, there being also slight lameness. The roof rapidly expanded, and every
other day the nut was moved on a bit to keep the cross-piece tight. I then had the
cross-piece bent downwards a little to prevent the nut pressing on the
rapidly-growing frog.[B] After another fortnight or so, I had a shoe made with
clips resting against the inside of the bars,[C] and the next time he was shod these
were also dispensed with. It is now a year ago since the animal recovered his frog,
and he still has the largest frog in the stable, and the hoof shows no sign of
contraction.’

[Footnote A: Ibid., vol. vi., p. 183]

[Footnote B: The italics are mine (H.C.R.).]

[Footnote C: The expanding shoe itself was here evidently dispensed with, and an
ordinary shoe with bar-clips used in its stead (H.C.R.).]

(b) De Fay’s.—Among other shoes of the expansion class may be
mentioned that of De Fay. Like the preceding, it is a shoe with a flat bearing
surface, and provided with bar-clips. It is, however, un hinged. The requisite
degree of periodic expansion is in this case arrived at by a forcible widening of the
heels of the shoe, accomplished by bending the substance of which it is made, and for
this purpose the instrument illustrated in Fig. 75 is employed.

The foot is first properly trimmed by levelling the heels and thinning the sole on
each side of the frog. The shoe is then fixed by nails in the ordinary manner, taking
care that the last nails come not too far back, and that the clips rest evenly and
firmly on the inside of the bars.

The dilator, hoof-spreader, or vice, as it is variously called, is then applied,
its two jaws (a and b) fitting against the inner edge of the shoe at
the heels. Careful note is taken of the width of the hoof as measured on the
graduated scale (e, e), and the double screw (g, h)
revolved by means of the wrench (k), until the opening of the jaws thus obtained
registers an expansion of 1/12 to 1/8 inch.

The dilatation is repeated at intervals of from eight to ten days, until, at the
expiration of a month or six weeks, the amount of total expansion of the heels
registers nearly an inch. That the method requires the greatest care may be gathered
from the reports of continental writers. They state that frequently the pain and
consequent lameness keep the patient confined to the stable for several days.

Numerous and but slightly differing forms of the dilator are on the market. As in
principle they are all essentially the same, and are to be found illustrated in any
reliable instrument catalogue, they need no description here.

FIG. 75.—DE FAY’S VICE.

(c) Hartmann’s.—A further useful expansion shoe is that of Hartmann’s
(Fig. 76), in that it may be adapted for either unilateral or bilateral contraction.
This shoe is also provided with bar-clips, and forcibly expanded at the heels by
means of a dilator. The expansion is governed by saw-cuts through the inner margin of
the shoe directed towards its outer margin, and running only partially through the
inner half of the web (see Fig. 76).

According as the contraction is confined to the inner or outer heel, the saw-cuts,
one or two in number, are placed to the inner or outer side of the toe-clip. When the
contraction is bilateral, the saw-cuts, one or more in number, are placed on each
side of the toe-clip.

(d) Broué’s.—This is one of the forms of so-called ‘slipper’
shoes (see Fig. 77). We have already indicated that the shape of the bearing surface
of the ordinary shoe—by its ‘seating’ or sloping from outside to
inside—is sometimes a cause of contraction. In the ‘slipper’ of Broué
this bearing is reversed, and the slope is from inside to outside. In the original
form of this shoe the slope to the outside was continued completely round the shoe.
Experience taught that the strain this enforced upon the junction of the wall with
the sole was injurious, and that the ‘reversed seating,’ if we may so term it, was
best confined to the hinder portions of the shoe’s branches.

FIG. 76. This figure illustrates the principle of the Hartmann expanding shoe.
a, a, The clips to catch the inside of the bars; b, c, saw-cuts.

The amount of slope should not be excessive. If it is, too rapid and too forcible
an expansion takes place, and pain and severe lameness results. Dollar gives the
requisite degree of incline by saying that the outer margin of the bearing surface of
the shoe should be from 1/12 to 1/8 inch lower than the inner.

In the case of the Broué slipper, it is the animal’s own weight that brings
about the widening of the heels, the slope or outward incline of the slipper simply
causing the inferior edge of the wall at the heels to spread itself outwards instead
of sliding inwards on the bearing surface of the shoe.

FIG. 77.—THE SLIPPER SHOE OF BROUÉ.

(e) Einsiedel’s.—Like the ‘slipper’ of Broué, the Einsiedel
shoe depends for its effects upon the slope of the bearing surface.

It differs from the Broué in being provided with a ‘bar-clip.’ This, in
addition to gripping the bars like the bar-clips of other expanding shoes, also
assists, under the body-weight, in expanding the heels by the pronounced slope given
to its upper surface. The expanding force exerted by the body-weight falls thus,
through the medium of the bar-clip, clip, partly upon the bars, instead of, as
in the Broué, solely upon the wall. We say partly advisedly, for, in
addition to the slope upon the outer side of the bar-clips, the bearing surface of
the heels of the shoe is slightly sloped outwards also. The good office served
by the bar-clip is the lessening of any tendency to strain upon the white line.

FIG. 78.—THE SLIPPER AND BAR-CLIP SHOE OF EINSIEDEL.

Those we have described by no means exhaust the number of expansion shoes that
have been devised. There are numerous others, many of which are composed of
three-hinged portions, the two hindermost of which are gradually separated by a
toothed arrangement of their inner margins and a travelling bar, the disadvantage of
which is that it is liable to work loose. In the majority of this class of shoe the
hinges are placed far forward, one on each side of the toe. They there become exposed
to excessive wear. In fact, against the bulk of this form of shoe it may be urged
that they cannot be worn by the animal at work, that they are expensive, difficult to
make, and easily put out of order.

3. By Operations on the Horn of the Wall.

(a) Thinning the Wall in the Region of the Quarters.—This is best
done by means of an ordinary farrier’s rasp. The thinning should lessen gradually
from the heel for 2-1/2 to 3 inches in a forward direction. That portion of the wall
next to the coronary border, about 1/2 inch in breadth, should not be touched. At
this point the thinning should commence, should be at its greatest, and lessen
gradually downwards until at the inferior margin of the wall the normal thickness of
horn is left. The animal is then shod with a bar shoe and the hoof bound with a
bandage soaked in a mixture of tar and grease, in order to keep the thinned portion
of the wall from cracking. In this condition the animal may remain at light
labour.

When possible, however, it is better to combine the thinning process thus
described with turning out to grass. In this case the ordinary shoe is first removed,
and the foot poulticed for twenty-four hours to render the horn soft. The foot is
then prepared by slightly lowering the heels—leaving the frog
untouched—and thinning the quarters in exactly the manner described above.

After this is done, the animal is shod with an ordinary tip, a sharp cantharides
blister applied to the coronet, and then turned out in a damp pasture. In this case
the object of the tip is to throw the weight on to the heels and quarters. The
thinned horn yields to the pressure thus applied, and a hoof with heels of a wider
pattern commences to grow down from the coronet. Two to three months’ rest is
necessary before the animal can again he put to work.[A]

[Footnote A: This is the treatment strongly advocated by A.A. Holcombe, D.V.S.,
Inspector, Bureau of Animal Industry, U.S.A.]

(b) Thinning the Wall in the Region of the Toe.—This is done with the
idea that the tendency of the heels to expand under pressure of the body-weight is
helped by the thinned portion at the toe allowing the heels to more readily open
behind. Seeing that in the case of toe sand-crack the converse is argued—that
contraction of the heels readily takes place and forces the sand-crack wider
open—it is doubtful whether this method is of any utility in treating
contracted heels.

(c) Grooving the Wall Vertically or Horizontally, and Shoeing with a Bar
Shoe.—Marking the wall with a series of grooves, each running in a more or
less vertical direction, was suggested to English veterinarians by Smith’s operation
for side-bones.

The manner of making the grooves, and the instruments necessary, will be found
fully described in Section C of Chapter X.

That the method is followed by satisfactory results the undermentioned case will
show:

‘A mare, which I have had in my possession since she was a foal, has always had
contracted feet, which were also unnaturally small…. Lately the mare has been going
very “short,” and at length her action was quite crippled. At times she was decidedly
lame on the off fore-foot. At no time have I been able to detect any sign of
structural disease. I thereupon concluded that the lameness was due to mechanical
pressure on the sensitive structures, and I determined to try the effects of the
above treatment. As this was my first experience of the process, I was careful to
carry it out in all its details, as described by Professor Smith. After the bar shoes
had been put on, the mare was very lame. I allowed her two days’ rest, then commenced
regular walking exercise, and she daily improved. After fourteen days there was no
lameness, but still short action. I thereupon gave the mare another week’s walking
exercise, at the expiration of which I drove her a short turn of five miles, which
she did quite well, and free from lameness. For three months I kept the saw-cuts open
to the coronet, and continued the bar shoes, keeping the mare at exercise, and giving
her occasionally a drive. She never liked the bar shoes, and I was glad when I could
discontinue them, which I did in the fourth month. When shod with the usual shoes the
complete success of the treatment was shown. I have now had her going with the
ordinary shoes for the past two or three months, and the improvement in the shape of
the feet is very marked; there is no lameness; the mare is free in movement, fast,
and spirited, whereas previously she was quite the reverse, and almost unfit to
drive.'[A]

[Footnote A: W.S. Adams, M.R.C.V.S., Veterinary Journal, vol. xxx., p.
19.]

This method, though but recently introduced to the English veterinary surgeon, is
by no means new. According to Zundel, it was recently made known on the Continent by
Weber, but was previously known and mentioned by Lagueriniere, Brognier, and Hurtrel
d’Arboval.

When the grooving is in a horizontal direction, a single incision is sufficient.
This is made 3/4 inch below the coronary margin of the wall, and parallel with it,
extending from the point of the heel for 2 or 3 inches in a forward direction. As in
the previous method, a bar shoe is applied, and the animal daily exercised. Thus
separated from the fixed and contracted portion of the wall below, the more elastic
coronet under pressure of the body-weight commences to bulge. The bulging is of such
an extent as to cause the new growing hoof from the top to considerably overhang the
contracted portion below, and cure of the condition results from the newly-expanded
wall above growing down in a normal direction.

This consideration of contracted heels may be concluded by drawing attention to
the advisability of always maintaining the horn of the wall in as soft and supple a
condition as is natural by the application of suitable hoof dressings.

A useful one for the purpose is that made with lard, to which has been added a
small quantity of wax or turpentine.

Especially should a dressing like this be used when the hoof is inclined to be
hard and brittle, and where tendency to contraction has already been noticed.

The application of a hoof ointment is also particularly indicated where the foot
is much exposed to dampness, where the animal is compelled to stand for long periods
upon a dry bedding, or where the bedding is of a substance calculated to have a
deleterious effect upon the horn.

This, in conjunction with correct shoeing, will probably serve to avoid the
necessity for more drastic measures at a later time.

(b) LOCAL OR CORONARY CONTRACTION.

Definition.—Contraction at the heels, confined to the horn
immediately succeeding that occupied by the coronary cushion. Really, the condition
is but a somewhat arbitrary subdivision of contracted hoof, as we have just described
it in general. For that reason we shall give it but very brief mention.

Symptoms.—In this case the horn of the heels, instead of running down
in a straight line from the coronary margin to the bearing surface of the wall,
presents a more or less distinct concavity (See Fig. 79, a, a).

As is the case with contraction considered as a whole, this deformity may affect
one or both heels; and during its first appearance, which is after the first few
shoeings, the animal may go distinctly lame.

Causes.—Coronary contraction may occur in hoofs of normal shape
immediately shoeing is commenced, and frog pressure with the ground removed. It is
far more likely to ensue, however, if the hoof is flat, with the heels low, and the
wall sloping. And with those predisposing circumstances it is that the horse goes
lame, and not with the hoof of normal shape.

Seeing, then, that this condition is largely dependent upon the shape of the foot,
we may, to some extent, regard it as hereditary. Seeing further, however, that it
only appears when shoeing is commenced, we may in a greater degree also regard it as
acquired. The lesson, therefore, that this and other forms of contraction should
teach us is the carefulness with which the shoeing should be superintended in a large
stud, or in any case where the animal is of more than ordinary value.

FIG. 79.—HOOF WITH LOCAL OR CORONARY CONTRACTION (AS INDICATED AT THE POINTS
a, a).

The explanation of the restricted nature of this form of contraction is simple
enough. We have only to refer to the lessons taught by the experiments of Lungwitz,
described in Chapter III., and the condition almost explains itself. We remember
that, briefly, the coronary margin of the wall resembles a closed elastic ring, which
yields and expands to local pressure, no matter how slight. We remember also that
removal of the counter-pressure of the frog with the ground tended to contraction of
the wall’s solar edge when weight was applied. Connect these two facts with the
experience that this form of contraction more often than not occurs in hoofs with
sloping heels, and we arrive at the following:

1. The excessive slope of the heels tends to throw a more than usual part of the
body-weight upon the posterior portion of the coronary margin of the wall, with a
consequent expansion of that part of the coronary margin implicated.

2. That the shoeing, in removing the counter-pressure of the frog with the ground,
is at the same time tending to bring about contraction of the lower portions of the
wall at the heels and quarters.

3. That this tendency to contraction will at first appear in the thinner portion
of the area of wall named—namely, in that immediately below the bulging
coronary margin.

We thus get the appearance depicted in Fig. 79—a contraction (a, a)
of the heels in the horn below the coronary margin, with the coronary margin itself
bulging above, and a hoof of apparently normal width below.

We say ‘apparently’ with a purpose, for, as actual measurements will show, the
wall near the solar edge is really contracting, for reasons which we have just
described connected with shoeing. Its ‘appearance’ of normal width is accounted for
thus: The contraction at a, a is caused by the dragging inwards of the
coronary cushion brought about by the sinking downwards of the plantar cushion, with
which body it will be remembered the coronary cushion is continuous. With the
constant dragging in and down of the coronary cushion there is given, to the
horn-secreting papillæ, studding both the lower third of its outer face and its
lowermost surface, a distinct ‘cant’ outwards. Below the lowermost limit of the
coronary cushion, then, by reason of the cant outwards of the coronary papillæ
in the situations mentioned, the horn of the wall takes a more outward direction than
normal, a fact which lessens in effect the contraction as a whole really going on. It
is interesting, too, to note that by this outward cant of the wall below, and the
bulging of the coronary margin above it, the contraction (a, a) is heightened
in effect, and caused to appear greater than really it is.

From what we have said it follows that contraction of the heels, excepting the
extreme coronary margin, is existent generally, and not confined solely to a,
a.

We have, then, in this condition, as we indicated at the commencement, but a phase
in the evolution of ordinary contracted heels, for, with the progress of the
contraction already existing at a, a, and below those points, it is only fair
to assume that with it falling in of the at present bulging coronary margin must
sooner or later occur, that, though expanded when compared with the wall below it, it
will be really contracted as compared with what it was once in that same foot.

We may therefore conclude this section by remarking that factors tending to
contraction of the heels in general are equally potent in the causation of contracted
coronet alone.

Treatment.—Exactly that described for contracted heels. Bearing in
mind that contracted coronary margin is but the onset of contracted heels, and that
its first exciting cause is that of removal of the ground-pressure upon the frog, the
most careful attention must be paid to the shoeing. The use of bar shoes, ordinary
frog pads, or heelless shoes and bar pads, are especially indicated, together with
abundant exercise. By these means the normal movements of expansion will be brought
into play, and the condition quickly remedied.

C. FLAT-FOOT.

Definition.—By this term is indicated a condition of the foot where
the natural concavity of the sole is absent.

Symptoms.—In the flat-foot the inferior edge of the wall, the sole,
and the frog, all lie more or less in the same plane. It is a condition observed far
more frequently in fore than in hind limbs, and is seen in connection with low heels,
more or less obliquity of the wall, and a tendency to contraction. The action of the
animal with flat feet is heavy, a result partly of the build of the foot, and partly
of the tenderness that soon comes on through the liability of the sole to constant
bruising.

FIG. 80. This figure represents the lower surface of a typical flat-foot. It
illustrates, too, the commencement of a condition we referred to in Section B of this
chapter—namely, the compression of the frog by the ingrowing heels (b) and bars
(a).

Causes.—Flat-foot is undoubtedly a congenital defect, and is seen
commonly in horses of a heavy, lymphatic type, and especially in those bred and
reared on low, marshy lands. It is thus a common condition of the fore-feet of the
Lincolnshire shire.

As might be expected, a foot of this description is far more prone to suffer from
the effects of shoeing than is the foot of normal shape, and regarded in this light
shoeing may be looked upon as, if not an actual cause, certainly a means of
aggravating the condition. Directly the shoe—or at any rate the ordinary
shoe—is applied, mischief commences. The frog is raised from the ground, and
the whole of the weight thrown on to the wall. The heels, already weak and inclined
to turn in, are unable to bear the strain. They turn in, and contraction
commences. This ‘turning in’ of the heels is favoured by the undue obliquity of the
wall. At the same time, the sole being archless, a certain amount of elasticity is
lost. The weight is thrown more on to the heels, and the os pedis slightly descends,
rendering the flatness of the sole even more marked than before. With the loss of
elasticity of the sole concussion makes itself more felt. The animal is easily lamed,
bruised sole becomes frequent, and corns sooner or later make their appearance.

Treatment.—Flat-foot is incurable. All that can be done is to pay
careful attention to the shoeing, and so prevent the condition from being aggravated.
In trimming the foot the sole should not be touched; the frog, too, should be left
alone, and the wall pared only so far as regards broken and jagged pieces.

The most suitable shoe is one moderately seated. If the seating is
excessive, and bearing allowed only on the wall, there is a tendency for the wall to
be pushed outwards, and for the sole to drop still further. On the other hand, if the
seating is insufficient, or the web of the shoe too wide, and too great a bearing
thus given to the sole, then we get, first, an undue pressure upon the last-named
portion of the foot a bruise, and, finally, lameness. The correct bearing should take
in the whole of the wall and the whole of the white line, and should just
impinge upon the sole. Above all, the heels of the shoe should be of full length,
otherwise, if the shoe is worn just a little too long, its heels are carried under
the sole of the foot, and by pressure there produce a corn.

If, with these precautions in shoeing flat-foot, tenderness still persists, a sole
of leather or gutta-percha must be used with the shoe.

D. PUMICED-FOOT, DROPPED SOLE, OR CONVEX SOLE.

Definition.—This term is applied to the foot when the shape of the
sole is comparable to the bottom of a saucer. When least marked it is really an
aggravated form of flat-foot.

Symptoms.—In pumiced-foot the sole projects beyond the level of the
wall. The obliquity of the latter is more marked than in the previous condition, and
progression, to a large extent, takes place upon the heels. In addition to its
deformity, the horn is greatly altered in quality, and, as the name ‘pumice’
indicates, is more or less porous in appearance, bulging, and brittle.

Causes.—As a general rule, it may be taken that pumiced-foot is a
sequel of previous disease, although in its least pronounced form it may occur as the
result of accidental or other causes, such as those described in the causation of
flat-foot.

Occurring in its most marked form, there is no gainsaying the fact that
pumiced-foot is a sequel of either acute or subacute laminitis. As we shall see when
we come to study that disease, the dropping of the sole is brought about by distinct
and easily-understood morbid processes affecting the sensitive structures. Briefly,
these morbid processes in laminitis may be described thus: The accumulated
inflammatory exudate, and in some cases pus, weakens and destroys the union between
the sensitive and insensitive laminæ. This separation, for reasons afterwards
to be explained, is greatest in the region of the toe. The os pedis, loosened from
its intimate attachment with the horny box, is dropped upon the sole, and the sole,
unable to bear the weight, commences to bulge below.

The altered character of the horn is accounted for by the inflammatory changes in
the sensitive laminæ and the papillæ of the keratogenous membrane
generally, for it follows as a matter of course that these tissues, themselves in a
diseased condition, must naturally produce a horn of a greatly altered and inferior
quality.

When following the subacute form of laminitis, the changes characterizing
pumiced-foot are slow in making their appearance. The animal at first goes short, and
the lameness thus indicated gradually becomes more severe, until the animal is no
longer able to work. The feet become hot and dry, the hoof loses its circular form,
and the growth of horn at the heels becomes excessive. At this stage the appearance
of bulging at the sole begins to make itself seen. Later, the outer surface of the
wall becomes ‘ringed’ or ‘ribbed,’ the rings being somewhat closely approximated in
the region of the toe, and the distance between them gradually widening towards the
heels. The wall too, especially in the region of the toe, instead of running in a
straight line from the coronary margin to the shoe, becomes concave. It is this
change, together with the appearance of the rings, that indicates the loosening of
the attachment of the os pedis to the wall, and its afterwards backward and downward
direction (see Fig. 124).

FIG. 81.—HOOF WITH THE RIBS OR RINGS CAUSED BY CHRONIC LAMINITIS.

As a sequel of acute laminitis, these changes make their appearance with
more or less suddenness, and are generally complicated in that they owe their
occurrence to the formation of pus within the horny box.

Treatment.—Pumiced-foot is always a serious condition. The animal is
useless for work upon hard roads or town pavings, and is of only limited utility for
slow work upon soft lands. The more serious form, that following acute laminitis, and
complicated by the presence of pus, we may regard as beyond hope of treatment.

With the more simple form of the condition, we may do much to render greater the
animal’s usefulness. The same principles as were applied to the shoeing of flat feet
will have to be observed here. Trimming or paring of any kind, save ‘straightening
up’ of the wall, must be severely discountenanced. A broad-webbed shoe, one that will
give a certain amount of cover to the sole, is indicated. As in the treatment of
flat-foot, however, direct pressure upon the sole must be avoided, and the shoe
‘seated.’ The ‘seating,’ however, should not commence from the absolute outer margin
of the shoe’s upper surface. A flat bearing should be given to the wall and
the white line, and the seating commenced at the sole.

We have already remarked on the increased growth of horn at the heels. It is in
this position, then, that will be found the greatest bearing surface for the shoe,
and it is wise, in this case, to have the heels of the shoe kept flat. In other
words, the ‘seating’ is not to be continued to the hindermost portion of the branches
of the shoe. By this means there may be obtained at each heel a good solid bearing of
from 2 to 3 inches, which would otherwise be lost.

Where the accompanying condition of the horn is bad enough to indicate it, a
leather sole should be used, beneath which has been packed a compress of tow and
grease, rendered more or less antiseptic by being mixed with tar.

Where the sole is exceedingly thin, and inclined to be easily wounded, and where
the hoof, by its brittleness, has become chipped and ragged at the lower margin of
the wall, it may perhaps be more advantageous to use, in place of the compress of
tow, the huflederkitt of Rotten. This is a leather-like, dark brown paste.
When warmed in hot water, or by itself, it becomes soft and plastic, and may readily
be pressed to the lower surface of the foot, so as to fill in all little cracks and
irregularities, and furnish a complete covering to the sole and frog, and to the
bearing surface of the wall. When cold it hardens, without losing the shape given to
it, into a hard, leather-like substance.

Treated in this way, the animal with pumiced feet may yet be capable of earning
his living at light labour or upon a farm.

E. ‘RINGED’ OR ‘RIBBED’ HOOF.

Definition.—A condition of the hoof in which the wall is marked by a
series of well-defined ridges in the horn, each ridge running parallel with the
coronary margin. They are known commonly as ‘grass rings,’ and may be easily
distinguished from the more grave condition we have alluded to as following
laminitis, by the mere fact that they do not, as do the laminitic rings, approximate
each other in the region of the toe, but that they run round the foot, as we have
already said, parallel with each other.

FIG. 82.—HOOF SHOWING THE RINGS IN THE HORN BROUGHT ABOUT BY PHYSIOLOGICAL
CAUSES.

Causes.—This condition is purely a physiological, and not a
pathological one, and the words of its more common name, ‘grass rings,’ sufficiently
indicate one of the most common causes. Anything tending to an alternate increase and
decrease in the secretion of horn from the coronet will bring it about. Thus, in an
animal at grass, with, according to the weather conditions, an alternate moistness
and dryness of the pasture, with its consequent influence on the horn secretion,
these rings nearly always appear. The effects of repeated blisters to the coronet
make themselves apparent in the same way, and testify to the efficacy of blisters in
this region in any case where an increased growth of horn is deemed necessary. From
this it is clear that the condition depends primarily upon the amount and condition
of the blood supplied to the coronary cushion. Thus, fluctuations in temperature
during a long-continued fever, or the effects of alternate heat and cold, or of
healthy exercise alternated with comparative idleness, will each rib the foot in much
the same manner.

Treatment.—The condition is so simple that we may almost regard it as
normal. Consequently, treatment of any kind is superfluous. Where constitutional
disturbance is exerting an influence upon either the quality or quantity of the blood
directed to the part, then, of course, attention must be paid to the disease from
which it is arising.

F. THE HOOF WITH BAD HORN.

Definition.—As the name indicates, we have in this condition an
abnormally dry state of the horn.

Symptoms.—These are obvious. The horn is hard, and when cut by the
farrier’s tools gives the impression of being baked hard and stony, the natural
polish of the external layer is wanting, and there is present, usually, a tendency to
contracted heels. With the dryness is a liability to fracture, especially at points
where the shoe is attached by the nails. As a consequence, the shoes are easily cast,
leading to splits in the direction of the horn fibres. These run dangerously near the
sensitive structures, giving rise in many cases to lameness. Even where pronounced
lameness is absent the action becomes short and ‘groggy,’ and the utmost care is
required in the shoeing to keep the animal at work.

Causes.—To a very great extent the condition is hereditary, and is
observed frequently in animals of the short, ‘cobby’ type. In ponies bred in the
Welsh and New Forest droves the condition is not uncommon, especially in the smaller
animals. Animals who have had their feet much in water—as, for instance, those
bred and reared on marshy soils—and afterwards transferred to the constant
dryness of stable bedding, are also particularly liable to this condition. It is
noticed, too, following the excessive use of unsuitable hoof-dressings, more
especially in cases where coat after coat of the dressing is applied without
occasionally removing the previous applications.

Treatment.—As a prophylactic, a good hoof-dressing is indicated. It
should not consist solely of grease, but should have mixed with it either wax,
turpentine, or tar.

Above all, careful shoeing should be insisted on, and the owner of an animal with
feet such as these will be well advised if he is recommended to have the shoeing
superintended by one well competent to direct it rightly. The foot should be trimmed
but lightly, always remembering that in a foot of this description the horn, in
addition to being brittle, is generally abnormally thin. Jagged or partly broken
pieces should be removed, and the bearing surface rendered as level as possible. The
foot should be carefully examined before punching the nail-holes in the shoe, and the
nail-holes afterwards placed so as to come opposite the soundest portions of horn.
The nails themselves should be as thin as is consistent with durability, and should
be driven as high up as possible.

On the least sign of undue wear the shoes should be removed, never, as is too
often done, allowing them to remain on so long that a portion breaks away. If, with
the laudable idea of not interfering with the horn more than is possible, this is
practised, the portion of the shoe breaking off is bound to tear away with it more or
less of the brittle horn to which it is attached.

Where the breaks in the horn are so large as to prevent a level bearing for the
shoe being obtained, the interstices should be filled up with one or other of the
preparations made for this purpose. One of the most suitable is that discovered by M.
Defay. By its means sand-cracks or other fractures of the horn may be durably
cemented up.

‘Even pieces of iron may be securely joined together by its means. The only
precaution for its successful application is the careful removal of all grease by
spirits of sal-ammoniac, sulphide of carbon, or ether. M. Defay makes no secret of
its composition, which is as follows: Take 1 part of coarsely-powdered gum-ammoniac,
and 2 parts of gutta-percha, in pieces the size of a hazel-nut. Put them in a
tin-lined vessel over a slow fire, and stir constantly until thoroughly mixed. Before
the thick, resinous mass gets cold mould it into sticks like sealing-wax. The cement
will keep for years, and when required for use it is only necessary to cut off a
sufficient quantity, and remelt it immediately before application. We have frequently
used this cement for the repair of seriously broken hoofs. It is so tenacious that it
will retain the nails by which the shoe is attached without tearing away from the
hoof.'[A]

[Footnote A: Veterinary Journal, vol. iii., p.71.]

Failing this, the bearing surface may be made level, and fractures repaired by
using the huflederkitt described in the treatment of pumiced sole.

(b) THE SPONGY HOOF.

Definition.—This is the opposite condition to the one we have just
described, and is characterized by the soft and non-resistant qualities of the
horn.

Symptoms.—Spongy hoof is quite common in animals that have large,
flat, and spreading feet—in fact, the two appear to run very much together. It
is a common defect in animals reared in marshy districts, and of a heavy, lymphatic
type. The Lincolnshire Shire, for instance, has often feet of this description, and,
the causative factors being in this case long-continued, render the feet extremely
predisposed to canker. The horn is distinctly soft to the knife, and has an
appearance more or less greasy. Animals with spongy feet are unfit for long journeys
on hard roads. When compelled to travel thus, the feet become hot and tender, and
lameness results. A mild form of laminitis, extending over a period of three or four
days, often follows on this enforced travelling on a hard road, more especially in
cases where the animal is ‘heavy topped,’ and the usual food of a highly stimulating
nature. In fact, it has been the author’s experience to meet with this condition
several times in the case of shire stallions doing a long walk daily upon hard roads,
with the weather hot and dry.

Treatment.—When a horse with spongy feet is shod for the first time,
care must be taken to avoid excessive paring of the sole, for already the natural
wear of the foot has been sufficient to keep the soft horn in a state of thinness.
For the same reason hot fitting of the shoe must not be indulged in for too long a
time. That common malpractice of the forge, ‘opening up the heels,’ must, in this
case, be especially guarded against, or the excessive paring of the frog and partial
removal of the bars that this operation consists in will lay the foot open to risk of
contraction. To begin with, the heels are naturally weak, and, once the bars are
removed, there is nothing to prevent them rapidly caving in towards the frog. Even
when carefully shod, a foot of this class is readily prone to contract directly the
animal is brought into the stable, and the horn commences to dry to excess. An
ordinary light shoe should be used, and the nails should be light and thin. They
should be driven carefully home, and the ‘clinching’ made as tight and secure as
possible.

G. CLUB-FOOT.

Definition.—Under this name we indicate all cases in which the horn
of the wall become straightened from above to below. It will, therefore, include all
conformations varying from the so-called ‘upright hoof,’ in which the toe forms an
angle of more than 60 degrees with the ground, to the badly ‘clubbed’ foot, in which
the horn at the toe forms a right angle with the ground, or is even directed
obliquely backwards and downwards, so that the coronary margin overhangs the solar
edge of the wall.

FIG. 83.—THE CLUB-FOOT.

Symptoms.—Even in its least pronounced form the condition is apparent
at a glance, the alteration in the angle formed by the hoof with the ground striking
the eye at once, and the heels, as compared with the toe, appearing much too high.
When the condition is slight, the wall of the toe is about twice as high as that of
the heels, while in the most marked form the toe and the heels may in height be
nearly equal (see Fig. 83). When congenital, but little interference with the action
is noticed. Such animals, by reason of their ‘stiltiness,’ are unfit for the saddle,
but at ordinary work will perform their duties equally well with the animal of
normal-shaped feet. When acquired as the result of overwork, of contracted tendons,
or other causes, however, the gait becomes stumbling and uncertain. The body-weight
is transferred from the heels to the anterior parts of the foot, and the shoe shows
undue signs of wear at the toe.

Causes.—Upright hoof is undoubtedly hereditary, and is even seen as a
natural conformation in the feet of asses and mules. When hereditary in the horse,
however, it is certainly a defect, and is associated commonly with an upright limb,
and a short, upright pastern (see Fig. 83).

Among other causes, we may enumerate sprains or wounds of the flexor tendons, or
any disease of the limbs for a long time preventing extension of the fetlock-joint,
such as sprains or injuries of the posterior ligaments of the limb, splints or
ringbones so placed as to interfere with the movements of the flexor tendons, or, in
the hind-limb, spavin, keeping for some months the fetlock in a state of flexion. In
the very young animal the condition may be induced by an improper paring of the
foot—cutting away too much at the toe, and allowing the heels to remain.

Treatment.—When the condition is congenital, no treatment at all is
indicated. It might, in fact, be said that interference would tend rather to minimize
than enhance the animal’s usefulness; for, in this case, the club-shaped feet are in
all probability due to faulty conformation above. In other words, the upright hoof is
in this instance but a natural result of the animal’s build, with which useful
interference is impossible.

Where the upright hoof is a consequence of excessive paring of the toe, or
insufficient removal of the heels, the condition may be remedied by directing
attention to those particulars, and preventing their continuance. At the same time, a
greater obliquity of the limb axis may be given by the use of a suitable shoe. The
shoe indicated is a short one, with thin heels and a thick toe. In some cases the
abnormality may be remedied by the use of a tip. Whatever method is adopted, care
must be taken not to attempt too positive a change in the direction of the limb at
one operation. The process must be gradual.

In cases where the abnormality has been brought about by wounds to the flexor
tendons, the alteration in the direction of the limb is often so great as to produce
‘knuckling over’ of the fetlock. This, to a very great extent, may be remedied by the
use of a shoe with calkins and an extended toe-piece (see Fig. 84).

FIG. 84.—THE SHOE WITH EXTENDED TOE-PIECE AND HIGH CALKINS.

With this shoe a certain amount of forced exercise is advisable, and at intervals
of about two weeks the calkins should be somewhat lowered, until the heels are
brought as close to the ground as is possible. In giving directions for this shoe to
be made the veterinary surgeon must, when referring to the length of the toe-piece,
be guided entirely by the condition of the case. Ordinarily, a suitable length is
from 3 to 4 inches. It is necessary also to warn the owner that, by reason of the
length projecting, the shoe is liable to be torn off.

Should the ‘knuckling over’ have become complicated by bony deposits round the
seat of the original injury, then a favourable modification of the condition is not
so likely to result.

The benefit to be derived from the shoe with an extended toe-piece in a case of
excessive knuckling is admirably shown in a brief report of a case, under the title
of ‘Hooked Foot,’ in vol. xiv. of the Veterinary Record, p. 716:

‘An eighteen months’ old filly showed a deformity of the third phalanx, resulting
in her walking with the front face of the hoof on the ground. The flexors were
apparently all right, and the bending back seemed to be due to contraction of the
ligaments of the joint and the sheath of the perforans.

‘On the ground of absence of contraction of the flexors, or atrophy and paralysis
of the extensors, the surgeon considered the lesion curable by simple
orthopædic measures. By means of an elongated toe-piece to the shoe and
calkins, which were shortened every fifteen days, the filly was completely cured in
seventy days.’

H. THE CROOKED FOOT.

(a) THE FOOT WITH UNEQUAL SIDES.

Definition.—The foot thus affected has one side of the wall higher
than the other.

Symptoms.—This deformity is the better recognised when the foot on
the floor is viewed from behind. In addition to the difference between the height of
the inner and outer heel is seen at once a deviation in the normal direction of the
horn. That of the higher side is distinctly more upright than that of the lower, and
runs from above downwards and inwards towards the axis of the foot, while the horn of
the lower side maintains its normal direction of downwards and outwards.

From what we have said before on contracted foot, this bending in of the wall of
the upright side will at once be recognised as a form of contraction. It is, in fact,
contraction confined to one-half of the foot only, and, as a result, the upright side
of the crooked foot is prone to the troubles arising from that condition. Corns are
frequent, and atrophy of that half of the frog on the affected side supervenes. With
the inflammatory changes accompanying these conditions we find the horn of the
affected side deteriorating in quality. It becomes dry and brittle, and extremely
liable to sand-crack. At the same time, thrush of the contracted frog begins to make
its appearance.

Causes.—More often than not this condition is a result of the
conformation of the limb. According as the build above inclines the animal to ‘turned
in’ or ‘turned out’ toes, so shall we have feet with a wall crooked inwards or
crooked outwards; and it may be mentioned here that the evil results inflicted on the
foot by ill-shaped limbs above will make themselves the more readily noticed when the
animal comes to be shod for any length of time. So long as a natural wear of the foot
is allowed, so long does it accommodate itself to the form of limb above. So soon,
however, as the shoe is applied, and a more or less equal (and in this case harmful)
wear by that means insisted on, so soon does this abnormal change in the height and
direction of the horn fibres begin to make itself seen.

While arising in the majority of instances from faulty conformation of the limb,
crooked feet may also be brought about by bad shoeing, or by unequal paring of the
foot, and, in a few cases, from unequal wear of the foot in a state of nature.

Treatment.—Although it may be taken as a rule that lowering of the
higher wall, even if persisted in at every shoeing, will do nothing towards remedying
the primary cause (viz., the evil conformation of the limb), yet it will serve to
keep the condition within reasonable limits. In this case, while removing so much of
the wall as is deemed necessary, care must be taken to leave uncut the sole and the
bar. Leaving these intact gives us two natural and very potent protections against
the contraction already mentioned as impending.

Where, by reason of the thinness of the horn or other causes, sufficient paring to
equalize the tread cannot be practised, then the same end may be arrived at by the
use of special shoes. That branch of the shoe applied to the half of the foot with
the lower wall should be thickened from above downwards. Or, on the same branch, may
be turned up a calkin of sufficient height for the purpose. Of the two methods the
first is preferable.

In any case, whether depending upon paring, or upon the use of a special shoe, the
animal should be sent to the forge quite often, for it is only by a well-directed,
and therefore constant, application of the principles here laid down that improvement
may be brought about.

When marked contraction of one-half of the foot is present, it will be best
treated with the expanding shoe of Hartmann, already described in the section of this
chapter dealing with contracted heels (see Fig. 76).

(b) THE CURVED HOOF.

Definition.—The hoof with the wall of one side convex, and that of
the opposite side concave. Fig. 85, showing the foot in section from side to side,
gives an exact idea of this malformation.

Causes.—As was the case with the condition previously described, this
abnormality finds its primary cause in an unequal distribution of weight due to vice
of conformation in the limb above, causing one side of the hoof to be higher than the
other. As a result of this, the wall that is inordinately increasing in height
commences to bulge outwardly (Fig. 85, a), while the opposite (Fig. 85,
b) becomes concave.

The same state of affairs may be occasioned in the forge by leaving one side of
the foot too high, and subjecting the other to excessive paring for several
consecutive shoeings.

Treatment.—In the main this condition may be regarded as a
long-standing and aggravated form of the foot with unequal sides. We may say at once,
therefore, that it is not so easily remedied as that simpler defect; that, although
identical principles will be followed in its treatment, cure must be a matter of some
considerable time.

FIG. 85.—SECTION THROUGH A CROOKED FOOT. a, The higher and convex
side of the wall; b, the lower and concave side of the wall

Again, we must look to successive parings of the wall of the higher side to bring
about a gradual return to the normal. At the same time, the tendency to contraction
of that side is counteracted by shoeing wide, and, if necessary, giving to the upper
surface of that branch of the shoe what we have termed elsewhere a ‘reversed
seating’—viz., an incline of its upper surface from within outwards.

CHAPTER VII

DISEASES ARISING FROM FAULTY
CONFORMATION

A. SAND-CRACK.

Definition.—A solution of continuity of the horn of the foot,
occurring usually in the wall, and following the direction of the horn fibres.

Classification.—It is usual to classify sand-cracks according
to—

(a) Their Position.—Toe-crack when occurring in the
middle line of the horn of the toe, and quarter-crack when occurring in the
horn of the quarters.

Sand-crack of the frog and sand-crack of the sole may also each be met with. They
are, however, of rare occurrence, and are seldom serious enough to merit special
attention.

The toe-crack is met with more often in the hind-foot than in the fore, while the
quarter-crack more often than not makes its appearance in the fore-foot, and is
there, as a rule, confined to the inner side. The reasons for these positions being
so affected we shall deal with when treating of the causes of sand-crack in general.
It is interesting to note that the portions of wall known as inside and outside toe
are seldom affected.

(b) Their Length.—Complete when they extend from the
coronary margin of the wall to its wearing edge; Incomplete when not so
extensive.

(c) Their Severity.—Simple when they occur in the horn
only, and do not implicate the sensitive structures beneath; Complicated when
deep enough to allow of laceration and subsequent inflammation of the keratogenous
membrane. Such complications may vary from a simple inflammation set up by laceration
and irritation of the sensitive structures by particles of dirt and grit that have
gained entrance through the crack, to other and more serious changes in the shape of
the formation of pus, hæmorrhage from the laminal vessels, caries of the os pedis, or
the development of a tumour-like growth of horn on the inner surface of the wall
known as a keraphyllocele.

(d) Their Duration.—Recent when newly formed;
old when of long standing.

(e) Their Starting-point.—This last distinction we make
ourselves, and, referring to cracks of the wall, term them high when
commencing from the coronary margin, low when starting from the bearing
surface.

Causes.—We have already classified sand-crack as a disease arising
from faulty conformation. Thus, in just so far as a predisposing build of body may be
handed down from parent to offspring, we may regard sand-crack as hereditary. If we
do so, however, we must afterwards make up our minds to sharply distinguish between
the sand-crack plainly brought about by accidental cause, and that occurring as a
result of hereditary evil conformation.

With regard to the latter, we need hardly say that feet with abnormally brittle
horn are extremely liable. But with this, as with many other affections of the feet,
we shall find it necessary to consider several causes acting in cooperation. In this
case, for instance, given the brittle horn, it becomes necessary to further look for
exciting causes of its fracture.

We will take conformation first. In the animal with turned-out toes a more than
fair share of the body-weight is imposed on the horn of the inner quarter. Here,
then, three causes exert their influence together: The horn is brittle; the wall of
the inner quarter is thinner than that of the outer; additional weight is imposed
upon it. Fracture results.

Take, again, the vice of contracted heels. Here, in the first place, we have a
variety of causes tending to bring about the contraction. With the contraction, and
its consequent pressure upon the sensitive structures in the region of the quarters
and the frog, has arisen a low type of inflammation. The horn of the part has become
dry and brittle. The exciting cause of its fracture is found in an excessive day’s
work upon a hard, dry road, with, perhaps, a suddenly-imposed improper distribution
of weight, due to treading upon a loose stone, or a succession of such evil transfers
of weight due to travelling upon a road that is rough in its whole extent.

In their turn, too, such defects of the feet as we have mentioned in the last
chapter—as, for example, the foot with the pumiced horn, the foot with
abnormally upright heels, or that which is upright on one side only, or
crooked—each offers a condition which is predisposing to the formation of a
sand-crack. In each case it wants but the uneven distribution of the body-weight,
which, as a matter of fact, some of these conditions themselves give, to bring about
a fracture.

Apart from the predisposition conferred by conformation, must be remembered the
simpler predisposing causes leading to brittleness of the hoof. We refer to the
after-effects of poulticing, the moving from pasture to stable, the emigration from a
damp to a dry climate, or the alternate changes from damp to dry in a temperate
region. Each may have a deteriorating influence upon the horn, rendering it liable to
the condition we are describing. Excessive dampness alone, especially when the animal
is called upon to labour at the drawing of heavy loads upon a rough road, is not
infrequently a cause. In this case the wet, together with the constant friction of
the sharp materials of which the road is made, serves to destroy the varnish-like
periople. The wet gains access to the inner structures of the wall, the agglutination
of the horn fibres is weakened, and fissures begin to appear.

Other causes of sand-crack are purely accidental. An animal at fast work
over-reaches. The secretion of horn at the injured coronet is interfered with, a
diminished supply at an isolated spot being the result. From this point grows down a
fissure in the wall.

An injury of the same character may also be sustained in various other
ways—treads from other animals when working in pairs, accidental wounding with
the stable-fork, blows of any kind, or a self-inflicted tread with the calkin of an
opposite foot—each with the same result.

So far as causation is concerned, toe-crack stands in a class almost by itself. It
is met with nearly always in a heavy animal in the hind-foot, and is directly
attributable to the force exerted in starting a heavy load.

Unskilful shoeing also plays a part in the causation of sand-crack. Removal of the
periople by excessive rasping of the wall is most certainly a predisposing cause.
Cracks, or their starting-points, may also be caused by using too wide a shoe, or by
the use of nails too large in the shank. Also, they may arise from unskilful fitting
of the toe-clip, especially in the hind-foot of a heavy animal. It must be admitted,
however, that the part shoeing plays in the causation of sand-crack is not a large
one; far more depends upon the state of the horn and the animal’s conformation than
upon the exciting cause.

So far, our observations on the causes of sand-crack have referred to that form
occurring in the wall. Sand-crack of the sole or frog we have already said is but
seldom met with, and then it is always in connection with some exceptionally
deteriorated quality of the horn, as in the case of badly pumiced feet, or occurs as
a result of direct injury. Extensive slit-like cuts in this region, when deep enough
to lacerate the keratogenous membrane, are sometimes followed by the growth of a
fissure in the horn, and what might almost be termed a permanent sand-crack results.
Such cuts may be occasioned by sharp flints, broken glass, or other sharp objects
picked up on the road, or may result from the animal treading on the toe-clip of a
partially cast shoe.

Symptoms.—In every case the fissure, or evidence of its commencement,
is a diagnostic symptom. It is well to remember, however, that this may be easily
overlooked, especially when the crack is one commencing at the coronary margin. The
reason is this: Sand-cracks in this position often commence in the wall proper, and
not in the periople. They may, in fact, be first observed as a fine separation of the
horn fibres immediately beneath the perioplic covering. A crack of this description
may even show hæmorrhage, and have been in existence for some time, without the
periople itself showing any lesion whatever. Thus, unless lameness is present, or a
more than specially keen search is directed to the parts in question, the sand-crack
goes undiscovered, until of greater dimensions.

Further, the fissure may be hidden, either accidentally or of set purpose. It may
be covered by the hair, filled in and covered over with mud, or intentionally
concealed by being ‘stopped’ with an artificial horn, with wax, or with gutta-percha,
or, as is more common, be hidden by the lavish application of a greasy
hoof-dressing.

In this latter connection it is well to warn the veterinary surgeon, especially
the beginner, when examining for soundness, to be keenly critical before passing an
animal who is presented with feet smothered with tar and grease or any other
dressing. More especially should this warning be heeded when examining any of the
heavier breeds of animal with an abundance of hair about the coronet.

Referring again to the search for the crack, it is well to know that with
toe-crack the fissure is the more readily seen when the foot is lifted from the
ground. With quarter-crack, on the other hand, the fissure is wider, and consequently
the easier detected with the foot bearing weight.

Although commencing in the insidious manner we have described, the lesion is not
thus often seen by the veterinary surgeon. Usually, the animal with sand-crack is
brought for his inspection when lameness has arisen from it. In this case the cause
for the lameness will reveal itself in the crack, which is now too large to escape
observation. The coronet is hot and tender to the touch, and a sensation of warmth is
sometimes conveyed to the hand by the horn of the surrounding parts of the wall. It
is hardly necessary to say that, with accompanying conditions such as these, the
sand-crack is a deep one.

Where the lameness is but slight, we may attribute it almost solely to the pain
occasioned by the mere wounding of the keratogenous membrane, and to no very
extensive inflammatory changes therein. By some authorities this is said to be due to
the pinching of the sensitive structures between the edges of the fissure in the
horny covering. In our opinion, however, pinching does not occur unless inflammatory
exudation into the sensitive structures adjoining the crack has led to sufficient
swelling to cause them to protrude. In other words, the movements of the horny box,
communicating themselves to the structures beneath, and so occasioning movement in
the wounded keratogenous membrane, are quite sufficient to give rise to the lameness
without actual pinching of the structures implicated.

The severity of the lameness will vary with the rapidity of the gait, and with the
character of the road upon which the animal is made to travel. For instance, many
animals in which the lameness is imperceptible at a walk become ‘dead’ lame at a fast
trot. It is sufficiently explained when one remembers the greater movements of
expansion and contraction of the posterior parts of the wall brought about by the
increase in the rate of progression. The same animal, too, will go distinctly more
lame upon a hard than upon a soft surface.

In like manner the lameness from toe-crack also varies in degree with the rate of
progression and the character of the travelling, though not to such a noticeable
extent as in the lameness from quarter-crack. A greater variation may in this case be
brought about by moving the animal on ascending and descending ground. Descending an
incline, with a more than ordinary share of the body-weight thus thrown upon the
heels, the lameness is most marked. The reason would appear to be that the greater
expansion of the wall of the heels thus brought about leads to a proportionate
contraction of the wall at the toe, especially at the edges of the crack, thus
causing undue pressure upon the exact spot of the wound in the sensitive structures.
Ascending—the weight in this case transferred from the posterior to the
anterior portion of the foot—the expansion of the heels becomes a contraction,
with a corresponding lessening of the contraction at the toe and a distinct decrease
in the lameness.

In the case of a deep but recent crack there is always more or less
hæmorrhage. This favours risk of infection of the lesion with pus-forming
organisms, and so leads to a more or less pronounced lameness, a degree of swelling,
heat and tenderness in the coronet above, and a certain amount of surgical fever.

The acute symptoms subdued, but the fissure still remaining, gives us the crack we
have classified as ‘old.’ This may in every case be distinguished from a more recent
lesion by the amount of thickening of the overhanging coronet, and the presence of an
increased quantity of sub-coronary horn in the region immediately about the crack. The
previous inflammatory changes in the adjoining sensitive structures have here led to
an increased secretion of horn, and a greater or less deposition of inflammatory
connective tissue in the wounded coronary cushion.

Sand-crack of the toe always follows the direction of the horn fibres. That of the
quarter, however, may on occasion run a course that is somewhat zigzag, first
following the direction of the horn fibres for a short distance, then travelling in a
horizontal direction, and finally continuing its course again in a line with the horn
fibres, commonly at a point posterior to that at which it commenced.

In a quarter-crack that is old, and when contraction of the heels exists (which in
this case it usually does), then will often be found overlapping of the edges of the
crack. The expansion of the wall brought about when the body-weight is on the heels,
cannot, by reason of the break in it, continue itself anterior to the crack. As a
consequence, repeated expansion of the wall posterior to the crack, with the portions
anterior to it in a state of enforced quiescence, leads in time to the posterior edge
of the crack coming to lie over that of the anterior.

Complications.—The first complication likely to arise in a case of
sand-crack is that attending simple laceration of the sensitive structures in a
deep lesion. With the laceration all the phenomena of a repairing inflammation
make their appearance. As a result, there is more or less heat according to the
degree of inflammatory hyperæmia, swelling according to the amount of
inflammatory exudate, and pain according to the amount of pressure the two foregoing
bring to bear on the nerves in the inflamed area.

A second and more serious complication is the greater inflammation set up by the
introduction into the crack of foreign substances. Small portions of gravel and
flint, both by the irritation set up by their friction and by the infection they
carry in with the dirt surrounding them, are responsible for the mischief.

When, from direct communication with the blood-stream, due to extensive
hæmorrhage, bacteria from the outside gain entrance, this simple inflammation
is further complicated by the formation of pus, or a limited gangrene of the
keratogenous membrane.

In cases of great severity the gangrene of the keratogenous membrane spreads until
the deeper structures are involved. We then get a necrosis (in the case of toe-crack)
of the extensor pedis, and sometimes caries of the os pedis.

In like manner the necrotic changes occurring under these circumstances may invade
the deeper structures in the region of quarter-crack. As a result of this, we may
have the starting-point of suppurating corn, or necrosis of the lateral
cartilage—in other words, cartilaginous quittor.

Commonly accompanying quarter-crack is the condition of contracted heels and
atrophied frog. Sometimes described as a complication of sand-crack, it appears to us
more rational to rather regard the sand-crack as a result or complication of the vice
of contraction.

The overlapping of the edges of the crack before referred to occasionally gives
rise to the condition known as false quittor. A probe or a director passed beneath
the overhanging ledge of horn reveals sometimes a fissure of 1 inch or considerably
more in depth, and quittor is diagnosed. A careful paring away of the overhanging
horn, however, reveals the true state of affairs, and exposes to view the original
cause of the mischief—a simple fissure in the wall.

A serious complication—one fortunately met with but rarely—is that of
keraphyllocele. This is a tumour-like growth of horn, varying in size from the
thickness of an ordinary quill pen to that of one’s middle finger, growing down from
the coronary cushion, and attached to the inner side of the wall of the hoof. With
this lameness is always present, and more or less deformity of the hoof results. This
condition will be found described at greater length in Chapter IX.

Prognosis.—In the case of sand-crack this should always be guarded.
It may be taken as a general rule that cracks commencing from the coronary margin are
more troublesome to deal with than those originating below. The reason is not far to
seek. They here affect the wall just where the bevel in it for the accommodation of
the coronary cushion has rendered it weakest. Not only is it weakest, but being more
resilient than the portions below it, it suffers more from the alternate movements of
expansion and contraction of the foot than does the horn below.

Although in many cases a cure of the existing crack may be easily accomplished,
regard should be paid to the possibility of its recurrence, either in the same
position or elsewhere. Really, in offering an opinion as to the future usefulness of
an animal so affected, a greater attention should be directed to the animal’s
conformation than to the crack itself. Where the vice of conformation giving rise to
it (as, for example, contracted heels or upright hoof) gives hope of being remedied,
then naturally it may be safely said that the liability to sand-crack goes with
it.

A like favourable prognosis may be given in the case of cracks occasioned by
purely accidental causes.

Ordinarily, however, cracks once commenced tend rather to increase than decrease
in size and severity. From being superficial and incomplete, they become complete and
deep, with every unfavourable circumstance that an increase in size and depth brings
with it.

This much, however, may be promised to the owner. A simple crack, even though
originating from the coronary margin, is, in the vast majority of cases, curable.
Under a rational treatment its increase in size may be prevented, and a sound wall
caused to grow down from the coronet.

Treatment.—The principles governing the treatment of sand-crack are
simple enough in themselves, if not always followed by success.

1. Preventive.

This, as a rule, does not suggest itself until a crack of greater or less extent
has made its appearance. Then, simultaneously with the treatment proper of the
lesion, preventive measures should be adopted, to aid both in the healing of the
fissure already present, and to ward off the occurrence of others that might be
likely to form. The hoof, if abnormally brittle, should be regularly dressed with a
suitable ointment (one containing glycerine for preference), and its horn kept as
nearly as possible in a normal condition. When the condition of the horn predisposing
to its fracture is brought about by excessive wet, then the appropriate preventive
measures to be adopted suggest themselves.

With regard to the lesion itself, we may term ‘preventive treatment’ all those
measures having for their object the prevention of increase in the size of the crack.
They are as follows:

(a) Blistering the Coronet.—In a simple case, where the crack is
superficial and close under the coronary margin of the wall, a sharp cantharides
blister to the coronet immediately above it will have the desired effect. An
increased secretion of horn is brought about, and by this simple means the crack
prevented from becoming longer. Very often this is all that is necessary. In fact, we
may say here that, no matter what other treatment is adopted, the simultaneous
application of a blister to the coronet is always beneficial. To derive full
advantages therefrom, the blistering should be repeated several times at intervals of
about a fortnight.

(b) Clamping the Crack.—When the services of a skilled smith are at
hand, one of the readiest methods of performing this is to draw the edges of the
crack together with an ordinary horse-nail.

On each side of the crack a small horizontal furrow is burned or cut into the
wall, leaving the horn for about 1/4 inch on each side of the crack intact. This
provides a groove for the ends of the clamping-nail to rest in, and brings them flush
with the outer surface of the wall. The nail is then driven carefully home through
the crack, and the pointed end grasped by the farrier’s pincers. The edges of the
crack are then drawn tightly together, and the nail firmly clenched.

FIG. 86.—THE SAND-CRACK FIRING-IRON.

‘The horse-nails are prepared in the ordinary way as for driving, with the
exception that each is pointed on the reverse side, to prevent puncturing the
sensitive structures. Before being used the nails are put in a vice, and the head
hammered to form a shoulder, to prevent their being driven too far into the wall, and
breaking out the hold.'[A]

[Footnote A: Veterinarian, vol. xlviii., p. 100.]

Before driving the nail some operators burn or bore a hole for it. Opinion seems
to differ as to whether this is at all necessary.

A method of clamping which, on account of its simplicity, has become greatly
popular, is that of Vachette. For this operation is needed the outfit depicted in
Figs. 86 and 87.

FIG. 87.—THE SAND-CRACK FORCEPS AND CLAMP.

With the special firing-iron (Fig. 86) an indentation, sufficiently large to admit
the points of the clamp (Fig. 87), is made on each side of the crack. The clamp is
then adjusted, and pressed home tight by means of the sand-crack forceps (Fig. 87).
According to the length of the crack, one, two, or three clamps may be necessary.
Another useful clamp, though far more complicated in its structure, is that of
Professor McGill (Fig. 88).

FIG. 88.—MCGILL’s SAND-CRACK CLAMP.

‘The object of this invention is to arrange on a spindle, which is screw-threaded
at one end with a right-hand thread and at the other with a left-hand thread, two
clips or clamps, free to travel on the thread, there being a nut between the two
which can be turned by a spanner. The clips are placed on the hoof, one on each side
of the sand-crack, the hoof being prepared to receive the instrument by filing a
groove or notch for the clamps to fit into, and by turning the nut on the screw the
clamps are brought towards each other, and the crack thus prevented from
spreading.'[A]

[Footnote A: Veterinarian, vol. lxi., p. 141.]

Still a further useful clamp is that of Koster. This is considerably broader than
the clamp of Vachette, and its gripping edges are provided with teeth (see Fig.
89).

As with the clamp of Vachette so with this, a groove is burned into the wall on
each side of the crack for the accommodation of the jaws of the instrument, and the
clamp itself pressed home by means of a special pair of forceps. This form of clamp
holds well, and has the advantage of securing a wider area of horn than that of
Vachette or McGill.

FIG. 89.—KOSTER’S SAND-CRACK CLAMP.

Clamping by any method should be advised or undertaken only under certain
conditions. The horn should be moderately strong, and the wall should be thick. This
practically restricts the use of the clamp to cracks of the toe, and it is there, as
a fact, they are found of most benefit. While burning the grooves for the clamp, and
while tightening the clamp itself, the animal’s foot should be on the ground and
bearing weight at the heels, thus insuring the greatest possible approximation of the
edges of the crack.

With all methods of clamping an untoward result is sometimes the formation of a
fresh crack at the point of insertion of the clamps.

(c) By the Use of Thin Metal Plates.—These are of use when the horn
of the wall is too thin to allow of clamping, and are therefore of especial use in
cracks of the quarters. The plates are made so as to cover the greater part of the
length of the lesion, and are fastened to the wall by two or more screws on either
side of the crack. It is an advantage to slightly let the plate into the wall by
means of fitting it hot. In a complicated crack the plate serves the further useful
purpose of holding in position antiseptic pledgets, and so keeping the lesion free
from dirt and grit.

(d) By Various Methods of bandaging the whole Circumference of the
Wall.—In our opinion this method of attempting to secure immobility of the
crack, and so prevent its extension, is not often followed by success. The main
objection to the method is that it subjects the whole of the wall to the same
pressure, and does not restrict the operation to the point at which it is required.
As in the case of the metal plate, however, this method has the advantage that
antiseptic dressings may be kept in position in the case of a complicated crack.

FIG. 90.—SAND-CRACK BELT.

The binding of the wall may be accomplished in two ways. The simpler of the two is
to merely apply the sand-crack belt depicted in Fig. 90. Beneath this should be
applied a compress of tar and tow or other material, and the whole tightened up and
kept in position by means of the buckle and strap. This method of binding admits of
after-tightening should it unfortunately work loose.

The older method of binding the wall, and one now often practised by the smith, is
to use a quantity of so-called ‘tar-band’ or other stout cord. With this the foot is
neatly bound after the manner of a cricket-bat handle, and all movement of the crack
apparently restricted. There is always a tendency, however, for such a dressing to
work loose, and in the case of a complicated crack it has the disadvantage of
permanently hiding from view the changes taking place in the discharge from the
fissure.

(e) By wedging the Crack.—This is the exact opposite of clamping.
Whereas in clamping we obtain immobility of the crack by keeping it fixed in the
position of greatest approximation of its edges, in wedging, the crack is rendered
free from movement by maintaining it in that position where its edges are most widely
separated. In this case the edges of the crack are pared smooth, the cavity
thoroughly cleansed, and a wedge of hard wood firmly driven in so as to fit exactly
the fissure.

On the face of it it appears that this procedure would really tend to force open
and so lengthen the crack, especially at its coronary extremity. What one should
really remember, however, is that the crack is not made wider than before, but
that it is simply maintained in a position occurring with every contraction of the
heels of the foot, when it is normally at its widest. Movement of the edges is
thereby stopped, the immediately surrounding structures are rested, and a new growth
of horn, free from crack, induced to grow down from the coronet.

This method of treatment only serves to emphasize the fact that, with a sand-crack
once formed, it is the constant movement of the parts that tends most to keep it in
existence, and not any particularly marked exertion of force.

Some practitioners, with the wedge, apply also a clamp, thus assuring additional
firmness and solidity to that portion of the wall under treatment.

The method of wedging is undoubtedly successful, if neatly performed.

(f) By Surgical Shoeing.—A partial rest is given to the affected
parts by easing the bearing of the shoe at the point required. This may be done
either by removal of part of the wall at the spot indicated, or by thinning the web
of the shoe in the same position. The former is the method usually practised.
Cessation of movement given in this way is, as we have already said, only partial;
for, while the effects of pressure and concussion from below are minimized, the crack
is still able to suffer from the movements of expansion and contraction of the foot.
Still, as an auxiliary to other treatments, ‘easing’ of the wall under the affected
part should always be practised.

FIG. 91.—THE BEARING ‘EASED’ BY REMOVAL OF THE WALL.

FIG. 92.—THE BEARING ‘EASED’ BY THINNING THE WEB OF THE SHOE.

Figs. 91 and 92 show respectively the manner of ‘easing’ by removal of the wall,
and by thinning the web of the shoe. In this connection it is necessary to point out
that on no account should ‘springing’ of the heels of the shoe be allowed. Fig. 93
illustrates the ill-practice.

In this case, when the entire weight is thrown on to the heels, the portion of
wall posterior to the crack is bound to participate unduly in the downward movement,
and so tend to widening of the crack at its highest point.

FIG. 93.—THE BEARING ‘EASED’ BY ‘SPRINGING’ THE HEEL OF THE SHOE.

We have already referred to the matter of ‘clips.’ In no case, whether the crack
be at the toe or in the quarters, should a clip be placed immediately below it. If
the crack is at the toe, the usual clip should be dispensed with, and a clip at each
side made to take its place. At the same time care should be taken to avoid throwing
the weight far forward. For that reason a shoe with calkins or with very high heels
should be removed, and a shoe with an ordinary flat web substituted.

In the case of quarter-crack, where the constant movement of the parts under
expansion and contraction of the foot makes itself most felt, it is wise to apply a
shoe with clips fitting moderately tight against the inside of the bars. By this
means movement will to a very large extent be curtailed.

Where a marked tendency to contraction is found, as is often the case with
quarter-crack, then the shoe with the clips may be rendered more marked in its
operation by giving to the outer face of each clip—that face applied to the
bar—a slope from above downwards and outwards. In other words, a slipper shoe
should be applied and the contraction given equally as much attention as the
sand-crack itself.

Where the crack is situated far back in the quarter, and easing of the bearing
cannot be accomplished without tending to spring the heels, then the most suitable
shoe is a bar shoe. With it the bearing may, of course, be eased in exactly the
position required, and the heels still allowed to take their fair share in bearing
the body-weight, and thus assist in closing the crack. The bar shoe, if properly
fitted, gives us also a bearing on the frog, and aids greatly in counteracting
contraction.

2. Curative.

(a) The Application of Dressings to the Lesion.—In the case of a
recent crack, deep, and attended with hæmorrhage, the foot should be thoroughly
cleansed. Where possible, a constant flow of cold water from a hose-pipe should be
allowed to run over the foot. By this means the inflammatory symptoms will be held in
check and pain prevented. Later the shoe may be eased at the required place, and a
blister applied to the coronet. This, with rest, will sometimes prove all that is
needed.

Should a crack be of old standing, and complicated by the presence of pus, a
course of hot poulticing will often prove of benefit. The poultice should be
medicated with any reliable disinfectant, and should be renewed, or at any rate
reheated, two or three times daily. The crack itself should be thoroughly cleaned
after the removal of each poultice, and a concentrated antiseptic solution—such
as Tuson’s spts. hydrarg. perchlor., carbolic acid, and water, (1 in 10) or liquor
zinci chlor.—poured into it. On discontinuing the poulticing, the strength of
the antiseptic solutions may be decreased, the parts rested by correct shoeing, and a
blister applied to the coronet as before.

If these measures alone should prove insufficient, then the surgeon will either
fall back on those we have just related, or proceed to methods next to be
described.

(b) Immobilizing the Crack by Means of grooving the Wall.—To our
minds, this is as ready and withal as successful a method of dealing with sand-crack
as has yet been devised. It may be done in a variety of ways: (1) By two grooves
arranged about the crack in the form of a V, as Fig. 94; (2) by a perpendicular
groove on either side of the crack, about 1 inch in distance from it, and parallel
with the horn fibres, as Fig. 95; (3) by a single horizontal groove at the extreme
upper limit of the crack; (4) by drawing two horizontal grooves, one at its upper and
one at its lower end (see Fig. 96).

In Figs. 94, 95, and 96 the thick black lines illustrate the positions of the
various grooves made with the firing-iron for the purpose of immobilizing a quarter
sand-crack.

The points to be observed in carrying out this line of treatment are simple
enough. In all cases see that the crack is rendered as clean as possible by the use
of suitable dressings, and if an excess of horn is present immediately around it, as
in the case of a long-standing and complicated lesion, have it thinned down by
rasping.

All that is then needed is one or two moderately sharp, flat firing-irons. The
groove is then burned into the horn in the positions indicated, and that portion of
the wall containing the sand-crack thus prevented from participating in the movements
of the foot. For our own part, we consider the V-shaped incision, or either of the
horizontal methods of grooving, preferable to lines running in the direction of the
horn fibres. With the latter there is certainly a greater tendency to the formation
of new cracks than with either of those we advocate. The V-shaped incision we
consider most suitable of all, for the reason that by its means a greater degree of
immobility is conferred upon the necessary portion of the wall.

Whichever method is adopted, care should be taken to carry the grooves deep enough
into the horn, taking them down as near as possible to the sensitive structures. At
the same time, especial care should be exercised in not carrying them too deep at
their extreme upper limit, or in that case the liability to the formation of fresh
cracks in those positions will be greatly increased. vAfter grooving, a sharp blister
should be applied to the coronet every three or four weeks, and the animal, if free
from lameness, put to work.

(c) By stripping away a V-shaped Portion of the Wall around the
Crack.—This method is only indicated when the crack is greatly complicated
by the presence of pus, or by the growth of adventitious horn on the inner surface of
the wall. A radical cure is thus obtained, but the animal for a longer time
incapacitated from work.

The operation is best performed by first grooving a line to connect the points
a and c (Fig. 97). This should run immediately under the coronary
margin of the wall, and should stop short of injuring the coronary cushion beneath.
Grooves forming the sides ab and bc of the triangular piece of horn are
next made, and the horn contained within the lines ab, bc, and ca,
carefully removed. The grooves are the easiest made by a cautious use of the
firing-iron. The greater thickness of the horn may thus be penetrated, and the
grooves afterwards carried to their full and requisite depth by the use of the
drawing-knife.

With the removal of the horn the diseased structures are exposed to view. All such
should be removed by a free use of the scalpel, and a suitable dressing afterwards
applied. A necessary factor in the treatment is the employment of pledgets of
antiseptic tow. With these the exposed tissues are covered, and the successive turns
of a bandage run tightly over them, so as to exert a moderate degree of pressure.
When hæmorrhage has accompanied the operation, this dressing should be removed
on the following day, the wound dressed, and the pledgets of tow and the bandage
renewed. Any after-dressing need only then be practised at intervals of a week.
Repair after this operation is rapid, and takes place both from the exposed
podophyllus membrane and from the coronary cushion.

FIG. 97. The dotted lines outline the V-shaped portion of wall to be removed in
the treatment of complicated toe-crack.

Fig. 98. The dotted lines indicate the portion of wall to be removed in the
complete operation for complicated toe-crack.

(d) By stripping the Wall from the Coronary Margin to its wearing Edge on
Either Side of the Crack.—This is merely a more extensive application of
the method just described, and is only indicated in a complete and
complicated crack that has refused to yield to other modes of treatment (see
Fig. 98).

As in the previous case, a groove is run from a to c. The grooves
ab and de are then continued to the lowermost edge of the wall, and the
whole of the wall within these points removed. To facilitate removal, the white line
should be grooved between the points b and d. After-treatment is
exactly the same as that just referred to.

B. CORNS.

Definition.—In veterinary surgery the term ‘corn’ is used to indicate
the changes following upon a bruise to that portion of the sensitive sole between the
wall and the bar. Usually they occur in the fore-feet, and are there found more often
in the inner than in the outer heel.

The changes are those depending upon the amount of hæmorrhage and the
accompanying inflammatory phenomena occasioned by the injury.

Thus, with the hæmorrhage we get ecchymosis, and consequent red staining of
the surrounding structures. As is the case with extravasations of blood elsewhere,
the hæmoglobin of the escaped corpuscles later undergoes a series of changes,
giving rise to a succession of brown, blue, greenish and yellowish coloration.

With the inflammation thereby set up we get swelling of the surrounding
bloodvessels, pain from the compression of the swollen structures within the
non-yielding hoof, and moistness as a result of the inflammatory exudate.

In a severe case the inflammation is complicated by the presence of pus.

Classification.—Putting on one side the classification of Lafosse
(natural and accidental), as perhaps wanting in correctness, seeing
that all are accidental, and disregarding the suggested divisions of Zundel
(corn of the sole and corn of the wall) as serving no
practical use, we believe, with Girard, that it is better to classify corns according
to the changes just described.

Following his system, we shall recognise three forms: (1) Dry, (2)
moist, (3) suppurating.

The dry corn is one in which the injury has fortunately been unattended
with excessive inflammatory changes, and where nothing but the coloration imparted to
the horn by the extravasated blood remains to indicate what has happened.

The moist corn is that in which a great amount of inflammatory exudate is
the most prominent symptom. It indicates an injury of comparatively recent
infliction.

The suppurating corn, as the name indicates, is a corn in which the
inflammatory changes are complicated by the presence of pus.

Causes.—The causes of corns we may consider under two
headings—namely, predisposing and exciting.

Predisposing Causes.—By the heading of this chapter we have already
intimated that corns are due to faulty conformation of the foot. It is, therefore,
merely a description of such shapes of foot as favour their formation that will need
mention here.

The wide, flat foot, with low heels, may be first considered. Here the posterior
portions of the sole, those portions between the wall and the bars, fall very largely
in the same plane as the wearing surface of the bars and the wall. As a consequence,
these portions of the sole are more prone to receive injury from stones and rough
roads and from the pressure of the shoe.

The low heels, too, favour a more than due proportion of the body-weight being
thrown on to the posterior parts of the foot. Two evils, both inclining to the
production of corn, result from this. In the first place, the sensitive structures of
the posterior portions of the foot are subjected to undue pressure from above;
secondly, the posterior half of the foot, by reason of the extra weight thrown upon
it, is exposed also to greater effects of concussion than normally it should meet.
Added to this we find that the abnormally flat condition of the sole has resulted in
a great loss of resiliency. With undue pressure above, and a loss of resiliency and
added effects of concussion below, the sensitive structures included between the
opposing pedal-bone and the horny sole are bound to suffer more or less bruising each
time the foot comes to the ground, especially if the animal is moved at a rapid
pace.

Writing here of the effects of pressure and concussion affords a fitting occasion
to mention the fact that corns occurring in feet affected with side-bones are always
worse than in feet with normal elastic cartilages. The explanation of this is simple,
for there can be no doubt that the loss of resiliency in the diseased cartilage is
only another aid to undue pressure and concussion. The sensitive structures are
pinched between unyielding bone above and practically unyielding horn below.

Feet with high and contracted heels are also predisposed to corn. The contraction
in this case interferes with the downward movements of the os pedis during
progression, while in a state of rest there is a more or less constant pressure upon
the sensitive structures, due to the correct downward displacement of the pedal-bone
being opposed by the amount of contraction present. In the contracted foot, too, the
nutrition of the vessels supplying the secretory apparatus of the horn is largely
interfered with. The horn loses its natural elasticity, fails to respond to the
normal movements of the parts within, and aids in the compression and laceration of
the sensitive structures.

Weak feet, with horn too thin to withstand the expansive movements continually
going on—in other words, feet with weak, spreading heels—are also prone
to suffer from corns. In this case the flatness induced by the spreading, and the
insufficient protection afforded by the thin horn, both combine to lay the sole open
to the effects of concussion and direct injury.

Brittle feet—feet with horn of undue dryness, by reason of the contraction
thus brought about—are, again, particularly subject to corn.

So also with long feet. Whether occurring as a natural deformity, or as the result
of insufficient paring, bruises of the sole in feet thus shaped are common. The
reason for this will be better understood when we come to deal with the shoeing.

Other and minor predisposing causes are those mainly referring to an unnatural
dryness of the hoof when animals reared in the country are put to work in large
towns. We here really get several predisposing causes combining. A sudden change is
made from a more or less moist condition underfoot to one excessively dry. The
character of the travelling is wholly altered from occasional work upon soft lands to
continual labour upon hard-paved roads. The horn is often exposed to the vicious
influences of unsuitable litter, the application of unsuitable dressings, and the
deleterious effects of the street mud of our cities. All these play their part in
determining a condition of the horn, rendering it open to receive the effects of the
more exciting causes which we shall next consider.

Exciting Causes.—Than the shoeing, no more frequent and exciting
cause of corn exists. Whatever the predisposing influences may be, it is the shoeing
that in nearly every case completes the list, and finally inflicts the injury.

The evils in this connection we shall consider under two headings—viz., (1)
the manner in which the foot is pared; (2) the make and fitting of the shoe.

First among the faulty preparations of the foot comes that of excessive thinning
of the sole, especially in the regions subject to corn. The farrier addicted to this
is not as a rule content to confine his operations to the sole alone. In addition,
the frog and the bars also suffer from the too lavish use of his knife. His main
object is doubtless that of giving a broad and open appearance to the foot. It
follows from this that his operations are confined more to the posterior than the
anterior parts of the foot, and that the toe is therefore left too long. This gives
us a combination of causes leading to pressure and bruises upon the sensitive
structures at the seat of corn.

By this unequal paring of the toe and the heels greater weight is thrown upon the
posterior half of the foot. What then happens to the structures thinned as we have
described is this: the pared frog, lessened in volume, does not meet the ground. It
therefore fails to expand laterally with weight, and cannot assist, as normally it
should, in aiding the heels generally in their movements of expansion. The weakened
bars and the thinned sole, meeting with no opposition from the frog, give downwards
and inwards with the body-weight at the precise moment these movements should be
directed mainly outwards. As a further result of non-resistance on the part of the
frog, this time in a lateral direction, the bars, the sole, and the wall at the heels
all contract at the exact time they should expand. The end result must mean abnormal
pressure and bruising of the sensitive structures in that particular region.
Naturally, also, the excessive thinning of the horn renders direct injury to the sole
from stones or other objects in the road far more probable.

For this one reason alone—the manner in which it favours the production of
corn—too great a condemnation cannot be placed upon excessive paring of the
sole, the bars, and the frog.

When corns are already present, as they may be from other causes, the same remarks
will again apply to excessive paring. It is the custom with many smiths to carefully
pare down the discoloured horn in every case of corn they meet with, and at the same
time to again weaken the bars and even part of the wall at the heels, with the
laudable idea of relieving pressure on the part diseased. After what has gone before,
we need hardly say that their well-meant efforts have a precisely opposite effect to
the one they intend.

The fitting of the shoe is, perhaps, to a greater extent responsible for the
causation of corn than is the paring we have just described.

A few of the evils connected with the shoe may, however, be justly described as
unavoidable. We must shoe; we cannot shoe and leave a normal foot!

A shoe excessively seated, especially from the last nail-hole backwards, may be
regarded as dangerous. In this case, with every application of the body-weight, there
is given to the foot a tendency to contract, especially at its lower margin. Result:
undue pressure upon the tissues around and the production of corn.

On the other hand, varying with the form of foot, the seating may be insufficient.
In the case of flat-foot, or dropped sole, for instance, insufficient seating will
lead to undue pressure of the web of the shoe upon the sole, and in that way bring
about bruising of the sensitive sole beneath.

Shoes with heels or calks too high, by destroying the counter-pressure of the frog
with the ground, serve to bring about a series of changes we have described under
contraction, and again result in pinching and bruising of the sensitive
structures.

The opposite excess—a shoe thick at the toe and thin at the heels—is
blamed by Zundel for causing a like injury. In our opinion, the reason this author
gives—namely, that the throwing of greater weight upon the heels leads to
bruising of the sensitive structures—can only correctly apply to a
wrongly-applied shoe of this type, and not to the shoe itself. True, a shoe
with a thick toe and thinned heels will throw an undue proportion of the body-weight
upon the heels if the foot is not properly prepared for it. A wise man, however, will
most certainly so cut down the toe for the reception of this shoe that, with the shoe
in position, there will still be maintained a tread that is normal. To our minds harm
is far more likely to arise from a shoe of this class through the thinned iron heels
of the shoe becoming attenuated under wear to the point of bending, and so inflicting
an injury upon the adjoining sole.

Similarly, this last remark with regard to the thinning of the heels of the shoe
will apply to a shoe with too broad a web. As the thinning of the shoe proceeds with
wear, the inner portion of the thinned branch is bent up on to the sole, and again
inflicts the injury.

The matter of bearing is also of importance when considering the causation of
corn. In a previous chapter we have already described the correct bearing as that
which includes the whole of the lower margin of the wall and the white line, and just
impinges on the sole. Any marked deviation from that will, if long continued, be
followed by injury to the foot.

With the bearing surface of the shoe too narrow—in contact with the wall
solely, or perhaps only a portion of it—it is evident that a large proportion
of the foot that should properly bear weight is thrown out of action. A heavy strain
is imposed on the white line, and undue descent of the sole and contraction of the
heels brought about. Again the result of this is compression and bruising of the
tissues around the seat of corn.

With its bearing surface too wide, the shoe immediately exerts direct pressure
upon the sole with every movement of the animal. The sole normally is not made to
receive this, and harm is bound to result.

Among other ill-fitting shoes we may mention the one with branches too short, and
the one with the extremities of the branches too pointed. In the first case, as wear
of the shoe proceeds, the thinned end is far more likely to turn in under the seat of
corn than is a shoe with branches of ordinarily correct length. It is evident in the
second case that the pointed branch, when thinned, is a more dangerous agent than the
branch which is nearer the square at its end.

The matter contained in the first half of the foregoing paragraph explains in a
large measure the rarity of corns in the hind-feet. Here there is nothing to prevent
a shoe with branches of full length being used. The correct bearing is thus
maintained, even with a shoe excessively thinned with wear, and the liability to
injury from it decreased. An exception is to be found in the case of a feather-edged
shoe, such as is used to prevent cutting or brushing. The thinning by wear from above
to below of the branch already purposely thinned from side to side leads to the
formation of a thin and narrow piece of iron admirably calculated to bend over and
injure the sole.

Even with a shoe of correct length, with a flat-bearing surface at the heels, and
other conditions favourable to correct application, evil may still result from the
shoe itself being made too narrow. As a result of this, the branch of each
side is set too far under the foot, with consequent injury to the sole. This is, of
course, sheer carelessness on the part of the smith. When practised, however, it is
not easy of detection, as in all cases the foot is rasped down to cover what has been
done. In other words, the foot is made to fit the shoe and not the shoe the foot.

Recognising this close fitting of the shoe as a cause, we are able to explain in
some measure how it is that corns should occur with greater frequency in the inner
than in the outer heel. There is no doubt that the inner branch of the shoe is nearly
always fitted closer than is the outer. In the fore-foot it is also often shorter.
Take these two evils and add to them the fact that the inner heel is called upon to
bear more of the body-weight than is the outer, and the frequency of corns in the
inner heel will no longer be wondered at.

Indirectly, the shoe may still be a cause of corn by reason of the irritation set
up by gravel and small pieces of flint becoming firmly fixed between the sole and the
web of the shoe. In nearly every case of this description the part to be injured is
the white line.

Corns may also result from the animal picking up a stone. The stone becomes firmly
wedged in between the inner border of the branch of the shoe and the bar or the frog.
With every step the animal takes it becomes wedged more tightly into position.
Projecting below the level of the lower surface of the shoe, it imparts the
concussion it thus obtains directly to the sole. A bruise—and a bad
bruise—is the result.

Finally, it cannot be denied that the work the horse is put to is largely
responsible for the causation of corn. In country animals corns are comparatively
rare, while in animals in town, almost constantly upon hard paving, they are common.
This seems to point strongly to the fact that concussion through constant work upon
unyielding roads is a great factor in their production.

Symptoms.—Unless the discoloration of the horn is accidentally
discovered by the smith, the simple, dry corn may go undetected. The disturbance
excited by it is so small, and the pain occasioned so slight, that the patient may
offer no indication of its existence.

Ordinarily, however, the first symptom is that of pain. The animal goes feelingly
with one or both feet, in some cases even showing decided lameness. The lameness,
however, is in no way diagnostic, and the lesion itself must be discovered before an
exact opinion can be pronounced.

As an aside, it is well to observe in this connection that a negative opinion as
to the existence of corn should never be given unless the superficial layers of horn
have first been removed with the knife.

When standing at rest the animal exhibits signs more or less common to all foot
lamenesses. He ‘points’ the foot—in other words, the limb is slightly advanced,
the fetlock partly flexed, and the heels from off the ground. When both feet are
affected they are pointed alternately, and the animal often manifests his uneasiness
by repeated pawing movements, and by scraping his bedding behind him.

Should the injury run on to suppuration, the lameness becomes most acute. The
pawing movements become more pronounced, and there is evident disinclination on the
part of the animal to place the foot squarely on the ground. One is then led to
manipulate the foot. The hoof is hot to the touch. Percussion causes the animal to
flinch, and to flinch particularly when that portion of the wall adjoining the corn
is struck. Finally, exploration with the knife reveals the serious extent to which
the injury has developed. In a neglected case of this description it is even possible
to detect the presence of pus by the amount of swelling and fluctuating condition of
the coronet. The suppurative process has advanced in the direction of least
resistance, and is on the point of breaking through the tissues immediately above the
horn.

Lameness due to corn is oftentimes intermittent. With a simple corn, dry or moist,
this intermission is largely dependent on the degree of dryness of the hoof or the
road, and also on the character of the road surface. With a neglected, suppurating
corn, on the other hand, variation in the degree of lameness, in addition to
depending on circumstances such as these, is dependent to a larger extent upon the
changes occurring with the suppuration. In this case the time of greatest lameness is
immediately before the pus gains outlet. Immediately after its exit at the coronet
the animal will go almost sound. Soundness continues so long as the opening at the
coronet remains clear. The tendency, however, is for the opening thus made to quickly
close again. Pus again accumulates, lameness arises as before, and disappears again
with the second discharge of the contents of the sinus now formed.

Pathological Anatomy.—When dealing with their classification we gave
in outline the main pathological changes to be met with in corns. It now only remains
to give the same matter in slightly greater detail.

In dry corn the changes we meet with are those accompanying blood
extravasation. From excessive compression of the parts, or from the effects of direct
injury, a portion of the sensitive sole has become lacerated. The escaping blood
stains the surrounding soft tissues after the manner of blood extravasation
elsewhere. If the escape of blood is sufficiently large, the horn fibres in the
immediate vicinity also are stained. It is this stain in the horn that is the direct
evidence of the injury, and is itself popularly known as the corn. It may vary in
size from quite a small spot to a broad patch as large as half a crown, while its
colour may be a uniform red, or a mottled red and white. The microscopic changes in
this connection are illustrated in Fig. 99.

FIG. 99.—HORIZONTAL SECTION OF A CORN. The section cut at about the base of
the papillæ of the sensitive sole. a, papillæ, with horn-cells
surrounding them; b, interpapillary or intertubular horn; c, hollow
spaces in the intertubular material filled with blood; d, a papilla and its
surrounding horn-cells filled with blood.

Ordinarily, this ecchymosis of the horny sole is due to injury of the sensitive
sole immediately beneath it. It may, however, proceed from injury to the
vessels of the laminæ either of the bars or of the wall. In this case the
ecchymosis of the horny sole may be explained by the fact that the escaped blood
tends to gravitate to that position.

When the corn is of long standing, or is due to repeated injuries on the
same spot, the horn adjacent to the lesion becomes hard and dry, and often abnormally
brittle, simply on account of the inflammatory changes thus kept in continuation.
This is often seen when attempts are made to pare out the corn with the
knife.

Should the injury be seated in the sensitive laminæ, then the brittle nature
of the horn secreted by the injured tissues makes itself apparent by the appearance
of cracks in the wall of the quarter. Why this should occur will be readily
understood by a reference to Fig. 100.

FIG. 100.—INNER SURFACE OF THE WALL OF THE QUARTER, SHOWING CHANGES IN THE
HORNY LAMINÆ BROUGHT ABOUT BY CHRONIC CORN.

It will here be seen that the injury to the keratogenous membrane has led to great
interference with the secretion of horn from the sensitive laminæ. As a result,
the regularly leaf-like arrangement of the horny laminæ has been largely broken
up. Certain of the laminæ are altogether wanting, while others are broken in
their length and rendered incomplete. With this condition there is always more or
less contraction of the quarter.

Microscopic examination of the structures involved in such a case reveals the fact
that with the contraction is an alteration in the normal direction of the horny and
sensitive laminæ.

They become bent backward, and, instead of the regular and normal arrangement
depicted in Fig. 32, show the distorted appearance given in Fig. 101.

From the appearances and characters of the blood-stain in the horny sole we are
able to deduce evidence relative to the duration and nature of the injury.

FIG. 101.—PERPENDICULAR SECTION OF THE WALL OF A CONTRACTED QUARTER IN A
CASE OF CHRONIC CORN. Both the sensitive and horny laminæ are bent backwards,
and hæmorrhages have taken place at the base of the sensitive laminæ.

When, for instance, the stain is not to be found in the superficial layers of the
sole, but is only discoverable by deep paring, then the injury is a recent one.

Where the stain is met with in the superficial layers of horn, and is
quickly pared out, then the injury has been inflicted some time before, and has not
been repeated. When, as is sometimes the case, layers of horn that are stained are
found alternated with layers that are healthy, then we have evidence that the cause
of the corn, whatever it may be, is not in constant operation.

Similar indication of the age of the injury is also afforded by the colour of the
lesion.

A stain that is deep red is proof that the injury is comparatively recent.

A distinct yellow or greenish tinge, on the other hand, is evidence that the
injury is an old one.

In the Moist Corn we have, in addition to the blood extravasation, the
outpouring of the inflammatory exudate. In the most superficial layer of the horn
this may not be noticeable. As one cuts deeper into the sole with the knife, however,
it will be found that the lower layers of horn are more or less infiltrated with the
discharge. This gives to the horn a soft consistence, a yellow appearance, and a
touch that is moist to the fingers.

With the accompanying inflammation the cells in the neighbourhood of the injury
are enfeebled and their normal functions interfered with. We may thus expect a
corresponding interference with the growth of horn. This is exactly what happens, and
as one cuts deeper still into the horn a point is finally reached when a well-marked
cavity is encountered. A pale yellow and usually watery exudate fills it. This cavity
points out the exact spot where the force of the injury has been greatest, where
death of certain cells of the keratogenous membrane has resulted, and where the
natural formation of horn has for a time been suspended.

In the Suppurating Corn, as in moist corn, we have pathological changes due
to the tissue reaction to the injury, plus the addition of pus organisms.
Confined within the horny box we have a discharge that, by reason of the living and
constantly multiplying elements it contains—the pus organisms—is always
increasing in bulk. This must be at the expense of the softer structures of the foot.
Accordingly, as the formation of pus increases, we get pressure upon and final
gangrene of the sensitive sole and of the sensitive laminæ of the bars and the
wall. With no outlet below, the pus formation increases until finally it finds its
way out of the hoof by emerging at the coronet.

This in some instances it may do by confining its necrotic influences solely to
the sensitive laminæ of the wall, in which case, if a dependent orifice is
quickly made at the sole, the injury to the laminæ is soon repaired by the
healthy tissue remaining.

In other cases, however, the necrosis has spread deeper. Caries of the os pedis,
of the lateral ligaments of the pedal-joint, or of the lateral cartilages, is a
result. When this occurs the exuding discharge from the coronet becomes thinner and
more putrescent, and its feel, when rubbed between the fingers, sometimes gritty with
minute fragments of broken-up bone. Here, unless operative measures prevent it,
necrosis soon spreads deeper still. The deeper portions of the os pedis become
affected. The capsular ligament of the joint is penetrated by the suppurative
process, and a condition of septic arthritis results. The cavity of the joint becomes
more or less tensely distended, according to the amount of drainage present, which in
this case is almost nil, with matter in a state of putrescence. As a consequence, the
surrounding ligaments become softened and yield, and the articular surfaces
displaced. The articular cartilages also suffer, become necrotic in patches, and
frequently wholly destroyed. The end result is one of anchylosis of the joint and
permanent lameness.

Prognosis.—With the ordinary dry corn a return to the normal may
nearly always be looked for. Similarly, with moist corn, and even with careful
treatment of the suppurating variety, the same favourable termination may be looked
for and promised.

What cannot so safely be assured is that a relapse will not occur. In other words,
the extent of the injury, no matter how serious, does not often offer anything that
cannot be overcome by Nature and careful surgery; but the conformation of the animal
does. A vicious predisposing conformation once there is there always, and although
the injury resulting from it may easily give way to correct treatment, the same
injury is bound to re-occur when the animal is again put to work.

Although with care suppurating corn, like other cases of suppuration within the
hoof, may yield to treatment, the owner of the animal should, nevertheless, be warned
that the condition is a serious one, especially should the joint become affected. It
may so happen, as sometimes in fact it does, that the animal may die as a result of
the infective fever so set up. From no surface in the body can absorption take place
quicker than from the synovial membrane of a joint. So soon, therefore, as this
membrane comes in contact with septic material, so soon does a severe septic fever
make its appearance. The septic matter has gained the blood-stream, and the patient
succumbs to septic poisoning.

Apart from death occurring naturally, the changes taking place in the joint in the
shape of bony growths or of actual anchylosis may be so severe as to render the
animal useless, and slaughter may have to be advised.

Treatment.—We have already said that by far the most active cause in
the production of corn is the shoe. It follows from this that it is to the shoeing we
must largely look for a successful means of their prevention, and that the treatment
of corn in its most simple form is really a matter for the smith, and not for the
veterinary surgeon.

The faults in connection with the shoeing we have mentioned fully when treating of
the causes of corn. From those we learn that a shoe with a flat-bearing
surface, or one moderately seated but flat at the heels, is the correct shoe for
nearly all feet. The heels of the shoe should not be too high, should not be too
short, and should be wide enough apart from each other to insure the wall of the foot
obtaining a fair share of the bearing. Finally, even with the present method of
shoeing, whenever it is possible to allow the frog to come to the ground, it should
be encouraged to do so, and excessive paring either of the latter organ or of the
bars or the sole should be strictly discountenanced. Where the sole is thin, or the
frog wasted, use a leather sole or a rubber pad. With these precautions, corns may be
prevented from occuring even in a foot with a predisposing conformation.

When corn is present, the first treatment usually adopted is that of ‘paring it
out.’ This is advocated by Percival and by many other writers. We cannot say,
however, that we agree with it—at any rate, not in the case of simple dry
corn.

‘Paring it out,’ and by that we mean thinning down the sole until close on the
sensitive structures, can only be advised in the case of suppurating corn, or in
cases where doubt exists as to whether pus is present or not. In the latter case
paring becomes necessary as an exploratory means to diagnosis.

When it appears fairly certain, even in the case of a moist corn, that pus does
not exist, then paring is to be discountenanced, for the reason that it only tends to
weakening of the parts and to assist largely in the corn’s recurrence.

Those who advocate it do so for the reason that it relieves pressure on the
injured parts.

That it does so directly from below cannot be denied; but that it also favours
contraction and compression from side to side is equally certain.

A moderate paring may, however, be indulged in, say, to about one-half the
estimated thickness of the sole. Softening of the horn and consequent lessening of
pressure may then be brought about by the use of oil, oil and glycerine, tincture of
creasote, or by poulticing.

In the case of a moist corn the paring should be stopped immediately the true
nature of the injury has made itself apparent. Warm poultices or hot baths should
then be used in order to soften the surrounding parts, lessen the pressure, and ease
the pain. After a day or two day’s poulticing, should pain still continue with any
symptom of severity, the formation of pus may be expected, and it is then time for
the paring to be carried further, until the question ‘pus or no pus?’ is definitely
settled.

Should the moisture be due simply to the presence of the inflammatory exudate,
then poulticing alone will have the desired effect, and the pain will be lessened.
With the decrease in pain the poulticing may be discontinued, and the horn over the
seat of the injury dressed with some antiseptic and hardening solution. Sulphate of
zinc, a mixture of sulphate of zinc and lead acetate, sulphate of copper, or the
mixture known as Villate’s solution,[A] may either of them be used. Suitably shod,
and with a leather sole for preference, the animal may then again be put to work.

[Footnote A: The composition of the escharotic liquid bearing his name was
published by M. Villate in 1829 as under:

Dissolve the salts in the acid, add little by little the subacetate of lead, and
well shake the mixture.]

When dealing with suppurating corn, then, a considerable paring away of the horn
of the sole becomes a matter of necessity. The freest possible exit should be given
to the pus, and this even when an opening has already occurred at the coronet. Unless
this is done, and done promptly, the putrescent matter still contained within the
hoof will make further inroads upon the soft structures therein, and later upon the
ligaments, and even bone itself.

Having given drainage to the lesion by the dependent orifice in the sole,
poulticing should again be resorted to and maintained for at least three or four
days. The poulticing may then be discontinued, and the openings in the sole injected
with a weak solution of Tuson’s spts. hydrarg. perchlor., a 1 in 20 solution of
carbolic acid, a solution of copper sulphate, with Villate’s solution, or with any
other combined antiseptic and astringent. The success of the treatment is soon seen
in the cessation of pain and in the decreased amount of discharge from the opening in
the sole.

Should pain unfortunately continue, the discharge remain, and a state of fever
reveal itself, then it may be understood that the suppurative process has not been
checked, that a portion of necrosed ligament, cartilage, or bone still remains,
which, surrounded as it is by pus organisms and putrefactive germs, is sufficient to
excite a constant irritation and maintain the internal structures in a state of
infection. In other words, we have what is known as a quittor.

This will call for deeper operation. The horn of the wall must be removed, and the
diseased structures, whether gangrenous keratogenous membrane, necrosed ligament, or
carious bone, carefully excised or curetted. This will be better understood by a
reference to the chapter on Quittor, where the means for carrying out the necessary
operative measures will be found described in detail.

Surgical Shoeing for Corn.—In the case of an ordinary dry corn, where
the injury has been definitely ascertained to be accidental, no alteration in the
shoeing will be necessary. Where, however, the corn is attended with a more than
ordinary degree of inflammation, or where for some reason or other excessive paring
has been practised, then it will become needful to shoe with a special shoe. The
object to be attained is the removal of pressure from that portion of the wall next
to the seat of corn.

The most simple shoe for effecting this is the ordinary three-quarter shoe. The
only way in which this differs from the ordinary shoe is that about an inch and a
half of that branch of the shoe adjoining the corn is cut off (Fig. 102). If at the
same time contraction of the heels exists, then, perhaps, a better shoe is that known
as the three-quarter bar (Fig. 103).

Or, if preferred, a complete bar shoe such as that described for sand-crack may be
used, and the upper portion of the web in contact with the foot at the seat of corn
thinned out so as to avoid pressure on the wall at this point. With this shoe we
shall at the same time supply a certain amount of pressure to the frog, and aid in
the healthy development of the part indirectly involved in the disease.

The same pressure may also be given to the frog, and protection afforded the sole,
by the use of a leather sole, or rubber pad on leather, as described when dealing
with contracted feet.

A further method of relieving pressure on this portion of the wall, without
removing the wall itself (a practice which should never be advised) is to make
certain alterations in the web of the shoe. This may be done in one of two ways.

FIG. 102.—THREE-QUARTER SHOE.

FIG. 103.—THREE-QUARTER BAR SHOE.

In the first, that portion of the bearing surface of the heel of the shoe is
‘dropped’ about 1/8 inch from the plane of the remainder, so that the shoe at this
position does not come into contact with the foot at all (see Fig. 104).

In the second case the shoe is what is termed ‘set’ at the heel. Here it is the
plane of the wearing surface of the shoe that is altered. The hinder portion
of the required heel is thinned so that its lower surface does not come into contact
with the ground. By this means the wall is freed from concussion and pressure. At the
same time the upper surface of the shoe is in contact with the wall of the foot (see
Fig. 105).

This ‘setting’ of the shoe is preferable to the method first described. It affords
a greater protection to the foot, and does not allow of fragments of stone and flint
getting in between the foot and the shoe, and so giving rise to further mischief.

The ‘set’ portion should be fitted full and long. It is obvious, too, that the
animal should not be allowed to carry the shoe too long; otherwise, as the other
portion of the shoe wears down to the level of the ‘set’ heel, pressure on the tender
part of the foot will again result.

FIG. 104.—SHOE WITH A ‘DROPPED’ HEEL.

FIG. 105.—SHOE WITH A ‘SET’ HEEL.

In applying surgical shoes for corn of long standing, it must be remembered that
the protection so afforded must be continued for some time. It is not sufficient to
see the lesion itself disappear. In addition to that there is also, in the majority
of cases, a certain amount of contraction to be overcome. This can only be done by
continuing the use of a leather sole or some form of frog or bar-pad as recommended
for the relief of that condition.

C. CHRONIC BRUISED SOLE.

A similar condition to that of corn may be met with in other positions on the
sole. It is described by Rogerson as sand-crack of the sole[A], and is invariably met
with around that portion of the sole in contact with the shoe.

[Footnote A: Veterinarian, vol. lxiii., p. 51.]

The animal is lame, and the shoe is removed in order to ascertain the cause.
Nothing at first is noticeable except that the animal flinches when pressure is
applied to the spot with the pincers, or the sole is tapped with the hammer.

On removing the sole with the knife, however, a distinct black mark is discovered,
which, when followed up by careful paring, is often found to have pus at the
bottom.

In this case the injury has resulted, as we have already intimated elsewhere, from
causing the animal to wear for too long a time a shoe with too broad a web or
insufficiently seated. Or it may have originated with the irritation set up by
foreign and hard substances between the web of the shoe and the foot.

In his description of this condition Mr. Rogerson draws attention to the fact that
the pus found should not be wrongly attributed to accidental pricking of the foot. He
says:

‘Considering that the cracks or splits are always found in the immediate vicinity
of the nail-holes, a certain amount of discretionary skill is required in order that
the lameness may be attributed to its proper cause. This is an instance in which the
presence of the veterinary surgeon is imperative, in order to prevent undue blame
being attached to the shoeing-smith. Misconception in these cases might very easily
arise when parties concerned are disposed to accept an unskilled opinion, sometimes
resulting in danger to the proprietor of the forge, not only of losing a shoeing
contract, but also of being involved in other ways which would probably prove even
more disastrous.

‘Horses that stand on sawdust or moss litter are sometimes found with extensive
discoloration of the horny sole in front of the frog. Their bedding material collects
in the shoe as snow does, and forms a mass, which keeps a continued and uneven
pressure upon the sole. A sound foot is not injuriously affected, but a very thin
sole is, and so also is a sole which has been bruised by a picked up stone. Even a
slight bruise becomes serious if pressure is allowed to remain active over the
injured part. Lameness increases, serous fluid is effused between the horn and
sensitive part, or even hæmorrhage may take place.'[A]

[Footnote A: Hunting, Veterinary Record, vol. xiv., p. 593.]

The Treatment of Chronic Bruised Sole offers no special difficulty. Removal
of the cause (in nearly every case incorrect bearing of the shoe) is the first
consideration. That done, the lesion may be searched for and treated in the ordinary
manner as described for corn. When pus is present it must, of course, be given exit,
and an antiseptic solution applied to the wound. Should the sensitive structures be
laid bare when allowing the pus to escape, then the wound so made should afterwards
be protected with a leather sole and antiseptic stopping.

CHAPTER VIII

WOUNDS OF THE KERATOGENOUS MEMBRANE

A. NAIL-BOUND—BIND OR TIGHT-NAILING.

Definition.—By the term ‘nail-bound’ is indicated that accident
occurring in the forge in which the nail of the shoe is driven too near the sensitive
structures. Although involving no actual wound, it is important to consider the
condition under the heading of this chapter, in order that it may be distinguished
from the graver accident of a ‘prick.’

Causes.—Very largely the whole matter of causation turns on the
correct fitting of the shoe. The points especially to be noticed in this connection
are (1) the position of the nail-holes in the web of the shoe, (2) the ‘pitch’ of the
nail-holes.

Regarding the position of the nails, it goes without saying that the first
consideration when ‘holing’ the shoe should be to punch the holes opposite to sound
horn. This remark applies especially to shelly and brittle feet, the type of feet in
which tight-nailing most often occurs. The next consideration in this connection is
that of punching the holes so that the nail emerges from the upper surface of the web
at exactly its correct point of entrance on the bearing surface of the foot. This
should be on the white line immediately where it joins the wall. From this position
any marked deviation inwards (‘fine-nailing,’ as it is termed) is bound to give to
the nail a direction dangerously near the sensitive structures.

The ‘pitch’ of the nail-holes should be such that the nail is guided more or less
nearly to follow the line of inclination of the wall. Accordingly, the nail-holes at
the toe should be ‘pitched’ distinctly inwards, the inward pitch lessening as the
quarters are reached, until the hindermost nail-hole or two is pitched in a direction
that is almost perpendicular.

Too great an inward inclination of the nail will, however, give rise to a
bind.

It is probable that ‘tight-nailing’ results more often from fine punching of the
shoe than from any fault in the pitch of the hole. Inattention to either detail,
however, is apt to bring the mischief about.

Even with a correctly fitted shoe, and with a normal foot, tight-nailing may occur
as a result of sheer carelessness on the part of the smith.

Symptoms.—Possibly the animal returns from the forge sound. It is on
the following day, as a rule, that evidence of the injury is given by the animal
coming out from the stable lame. In a well-marked case the foot is warmer to the hand
than its fellow, and percussion over the wall will sometimes reveal the particular
nail that is the cause of the trouble. Should the shoe be removed, then the fact that
the hole the nail has made is far too close to the sole often points out at once the
seat of the mischief.

Treatment. As to whether or not the shoe should be removed is very much a
matter for careful discretion on the part of the veterinary surgeon. Where the foot
is shelly and brittle even a good smith sometimes finds himself unable to firmly
attach the shoe without verging closely on causing the condition we are now
describing. The author has known cases where animals with feet of this description
have almost invariably returned from the forge, or rather been found the next day,
with a suspicion of tenderness. After the lapse of a day or two this has quite often
disappeared, and nothing in the meantime been done with the foot. Seeing, therefore,
that removal and refitting of the shoe is in this case attended with risk of breaking
away portions of the brittle horn, and so rendering the foot in an even worse
condition than it was before, it is policy to decline to have the shoes removed
unless worse symptoms make their appearance.

In coming to this decision the veterinary surgeon must be guided by noting in the
wall the points of exit of the nails. Should the nail adjoining the position already
pronounced to be tender have come out at a higher point than the others, it may be
assumed that at a lower position in its course through the horn it has gone near the
sensitive structures without actually penetrating the horny box, and that in the
course of a day or two the sensitive structures involved will accommodate themselves
to the pressure thus inflicted.

If, on the other hand, symptoms of tight-nailing show themselves in an animal with
good sound feet, then there is no objection to be raised against having the shoe at
once removed. Should the offending nail be definitely detected, then the shoe may
again be put on, and that particular nail omitted from the set.

B. PUNCTURED FOOT.

(Pricked Foot—Nail-tread—Gathered Nail.)

Definition.—Under this heading we propose describing wounds of the
foot occurring in the sole or in the frog, and penetrating the sensitive structures
beneath.

Causes.—These we shall consider under two headings:

1. Wounds resulting from the animal himself ‘picking-up’ or ‘treading’ on the
offending object.

2. Cases of pricking in the forge.

Those occurring under the first heading are, of course, purely accidental. In the
majority of cases, the object picked up is a nail; but similar injury may result from
the animal treading on sharp pieces of wood or iron, on pieces of umbrella wire, on
pointed pieces of bones, broken-off stable-fork points, sharp pieces of flint, etc.
The same accident may also occur in the forge as a result of the animal treading on
the stumps of nails, from treading on an upturned shoe with the stumps of nails in
situ, or from treading on an upturned toe-clip. It may also occur from an
accidental prick with the stable-fork when ‘bedding up,’ or from casting part of a
shoe when on the road and treading on the nails, in this case left sometimes partly
in and partly out of the horn.

‘Serious wounds of this description are also met with in animals engaged in
carting timber from plantations in which brushwood has recently been cut down. This
is, of course, from treading on the stake-like points that are left close to the
ground. Hunters also meet with the same class of injury when passing through
plantations or over hedge banks, where the hedge has just been laid low or cut
down.

‘Agricultural horses also meet with severe wounds of this class from treading on
an upturned harrow.'[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. iv.,
p. 2.]

It has been remarked how strange it is that nails should so readily penetrate the
comparatively hard covering of the foot. The matter, however, admits of explanation.
One knows from common observation how easy it is to tilt a nail with its point
upwards by exerting a pressure in a more or less slanting direction upon its head.
This is exactly the form of pressure that is no doubt put upon the nail if the animal
treads upon it when moving at any pace out of a walk. The foot in its movement
forward tilts the nail up, and almost simultaneously puts weight upon it. The great
weight of the animal is then quite sufficient to account for its ready
penetration.

In purely country districts cases of punctured foot are of far less frequent
occurrence than in large towns. In the latter, animals labouring in yards where a
quantity of packing is done, or engaged in carting refuse containing such objects as
we have mentioned, or broken pieces of earthenware or glass bottles, meet with it
constantly.

For the manner of causation of those wounds to the foot occurring in the forge the
reader may be referred to the matter under the heading of ‘nail-bound.’ As in that
case so in this the nail may be wrongly directed by improper fitting of the shoe, by
the ‘pitch’ of the hole, or by the position of the hole. The nails may also be
wrongly directed as a result of faulty pointing, or by meeting with the stump of a
nail that has carelessly been allowed to remain in the substance of the horn.

Often pricking is a result of carelessness engendered by a rush of work. Often it
is almost unavoidable on account of the character of the foot that is brought to be
shod. Feet with thin horn, especially a thin sole, feet with horn shelly and brittle,
each in their way are difficult to shoe.

Sometimes pricking is purely accidental, as in the case of a ‘split’ nail. The
nail as it is driven splits at its point, and continues to split down its centre, one
half emerging at the correct spot on the wall, the other half bending inwards, and
penetrating the sensitive structures.

Common Situations of the Wound.—In a case of picked-up nail the
common seat of puncture is about the point of the frog, either in one of the lateral
lacunæ, in the median lacuna, or the apex of the frog itself. In comparison
with this puncture of the sole is rare.

Prick sustained at the hands of the smith may, of course, run in either of the
following directions: (1) Directly into the position where the horny and sensitive
laminæ interleave; (2) between the sensitive laminæ and the os pedis; (3)
into the os pedis itself; (4) the nail may bend excessively immediately after
entering the horn, and so pass either between the horny and sensitive sole; or (5)
between the sensitive sole and the bone.

Classification.—Punctured wounds of the foot may be classified as
follows:

Simple or superficial when penetrating no structure of great importance.
For instance, a prick that penetrates to the sensitive sole and is not driven with
sufficient force to seriously injure the os pedis we may regard as simple. In the
same manner a prick to the frog that, although deep, is mainly concerned with
penetrating the plantar cushion may also be classed as simple.

Deep or penetrating when driven with sufficient force or in such a
direction as to injure structures whose penetration is calculated to give rise either
to serious constitutional disturbance or to permanent lameness. In this category we
may place injuries to the terminal portion of the perforans, puncture of the
navicular bursa, fracture of the navicular bone and penetration of the pedal
articulation, and splintering of the os pedis.

Symptoms and Diagnosis.—While discussing the symptoms and diagnosis,
we will still continue to consider our subject under the two headings of (1)
accidental ‘gathering’ of some foreign body, and (2) pricks inflicted in the
forge.

In a few cases belonging to the former class the veterinary surgeon is fortunate
in obtaining a direct history of the injury. The driver has seen the animal go
suddenly lame, and has examined the foot for the cause. Either the nail has been
found embedded in the horn, or the puncture it has made detected, and the matter has
been reported. The foot is then explored and the full extent of the injury
ascertained.

In many cases, however, it so happens that no evidence of the infliction of the
injury is forthcoming. The momentary lameness occurring at the time of the prick is
unreported at the time by the attendant, and the horse for a time goes sound. It is
not until the changes set up by the subsequent inflammatory phenomena make their
appearance, and lameness results, that attention is called to the foot. When this
happens there has, as a rule, been time for pus to form around the seat of
puncture—a matter of about forty-eight hours.

The horse is now brought out for the veterinary surgeon’s examination, going
distinctly lame. If the case is well marked there may then be noted by the man of
experience many little signs pointing to the foot as the seat of the lameness. These,
though well enough known to the practitioner, are nevertheless difficult to describe.
It is, in fact, hard to say exactly in what they really consist, appearing to be as
much a matter of intuition as of actual observation.

There is a peculiar ‘feeling’ characteristic in the gait. The affected foot is put
forward fearlessly enough, but is not nearly so rapidly put to the ground. When at
rest the foot is almost immediately pointed, and the pain at intervals manifested by
pawing movements. It is this extreme liberty of the rest of the limb, as evinced
during the pawing movements, that really strikes one. Shoulder, elbow, knee, and
fetlock are all easily and painlessly flexed and extended. There is nothing wrong
with them; it must be the foot. The short manipulation necessary to test the
lameness—viz., the walk and slow trot—is sufficient to raise the animal’s
pulse and quicken the breathing.

All this is enough, and more than enough, to lead the veterinary surgeon to
examine the foot. It is hot to the touch, and at the coronet tender to pressure,
possibly in a neglected case fluctuating at the heel. Pain is evinced by the animal
withdrawing his foot when percussion takes place over the affected spot. In a bad
case one gentle tap is all that is needed. The animal at once snatches away his foot,
holds it high from the ground, and makes pawing movements in the air. At that moment,
too, his countenance is highly expressive of the pain he is suffering. Again the foot
is explored, the injury found, and the pus liberated.

Regarding the manner of exploration of the foot we will take first that case in
which the veterinary surgeon is called in early, and in which pus has not yet had
time to form. Sometimes the merest cleaning up of the inferior surface of the foot
then reveals a distinct stab either in the sole or the frog.

If the accident be recent only a little blood will be found, either liquid, or
coagulated about the wound. Later there exudes from the stab a flow of yellow, serous
fluid. The opening thus found should be carefully probed, and its depth and situation
noted.

At other times the prick is not so readily apparent. The nail or other object has
penetrated and afterwards withdrawn itself. The natural elasticity of the horn,
especially that of the frog, causes it to contract upon the puncture, and to largely
obliterate the hole made. What, therefore, may look to be but a simple injury to the
horn alone may in reality be the only evidence of a stab complicating the sensitive
structures. It thus behoves the veterinary surgeon to follow up and carefully cut out
any unnatural-looking mark in the horn, more especially if the horn is discoloured,
or if blood is extravasated into its fibres, or there is moisture exuding from the
part.

In some cases of this description the knife in the act of paring comes into
contact with the cause of the trouble. Sometimes this is a nail, sometimes a sharp
and small piece of flint, so deeply penetrated as to have become quite buried. When
met with in this manner, however, the foreign body is more often than not a splinter
of wood deeply embedded in the cleft of the frog or in the frog itself.

The fact that multiple punctures may occur should here be remembered, and the
remainder of the inferior surface of the foot thinly pared.

On withdrawal of the foreign object blood may immediately follow. Should the
former have been fixed in position for some time, however, pus is nearly always found
at the bottom of the wound. As a rule, its removal is comparatively easy, but one
case recalls itself to the author’s mind in which the extraction was a matter of
considerable difficulty. The offending object was a large, flat-headed nail, some 2
inches long. This was driven fast into the os pedis, and necessitated the employment
of a pair of pincers and the exertion of some amount of force to move it from its
position.

In this connection it must be remembered that the penetrating object sometimes
breaks off after entering the foot. The fact that this occasionally happens only
serves to give point to the advice we have previously rendered—that every stab
should be carefully probed, and its exact condition and depth ascertained.

In those cases where percussion has led to the positive opinion that pus really
exists, then the exploration must be most searching. There may, or may not, be a
suspicious-looking mark to work on. In the latter case, the veterinary surgeon must
not be content with confining his paring operations to one spot. The sole should be
carefully thinned all round, and the thinning cautiously proceeded with until either
small, pin-point hæmorrhages denote that healthy sensitive structures have been
reached, or a sudden flow of pus indicates that the injury has been definitely
located.

While the symptoms remain much about the same, the diagnosis of pricks received in
the forge, as compared with those occurring in the natural manner, is easy. The
animal starts to the forge quite sound, and returns, perhaps, with a slight limp. The
slight limp in two days’ time becomes a decided lameness, and no doubt remains as to
what has occurred. The mere fact of the lameness arising immediately after a visit to
the forge should be sufficient in the majority of cases to lead one to a correct
diagnosis.

Where the opinion has been formed that a prick has been received, then the shoe
should be removed.

This operation should always be superintended by the veterinary surgeon himself.
After the removal of the clinches, the nails should be drawn one at a time with the
pincers, and carefully examined. Often the offending nail may thus be picked out by
observing upon it blood-stains, or the moisture from inflammatory exudate or from
pus. Further inflammation will also be gathered by occasionally meeting with a nail
that has split.

At this stage, too, the veterinary surgeon should have noticed whether or not the
smith has previously sent the animal home with what is known as a ‘draw back.’ He has
discovered, immediately after he has done it, that he has pricked the animal. He has
then withdrawn the nail, and either sent the animal back with that nail altogether
missing from the set in the shoe, or with the hole filled up with a stump.

The shoe once off, the holes made by the nails in the horn should be minutely
examined for the presence of hæmorrhage, inflammatory fluid, or pus exuding
from them, and also for evidence of their correct placing in the foot. Should fluid
matter issue from any one of them, or should it be deemed that one has approached too
near the inner margin of the white line, more especially if tenderness exists around
it, that hole should be followed up with a ‘searcher’ or small drawing-knife until
diagnosis is certain.

Complications.—Before proceeding to discuss the complications that
may arise in the case of pricked foot, we may call to mind that the anatomy of the
parts teaches us that the most serious position in which a punctured wound can occur
is at the centre of the foot. Here the plantar aponeurosis, the navicular bursa, the
navicular bone itself, or the pedal articulation may be injured.

Anterior to this position the most serious mischief that can ordinarily result is
stabbing of the os pedis.

Posterior to the position we have named, the only structure to be injured is the
plantar cushion.

Anatomically, then, the inferior surface of the foot may be divided into three
zones, as follows:

A. Anterior, extending from the toe to the point of the frog.

B. Middle, extending from the point of the frog to the commencement of its
median lacuna.

C. Posterior, including everything posterior to the middle zone. This
division of the inferior surface of the foot into zones will be somewhat of a guide
also when describing the complications next to follow:

(a) Suppuration.—This is the common complication of most
wounds of the foot. When detected, it calls for immediate surgical interference in
the shape of removal of the horn of the sole or the frog, as the case may be. This we
shall consider further under the treatment.

(b) Separation of the Horny Frog.—This is a sequel to pus
formation in the sensitive structures immediately beneath it, and the condition makes
itself apparent by a line of separation between the horn and the skin of the heel of
the injured side.

(c) Wounding of the Plantar Aponeurosis.—This occurs when a
moderately-deep penetration of the horn of the middle zone has taken place. It is
always most painful, especially when complicated by necrosis. The heel is then
persistently elevated, and lameness is extreme, in some cases so severe as to cause
the leg to be carried altogether.

In favourable cases the necrosed piece of tendon is sloughed off by the process of
suppuration, and escapes with the discharges from the wound. There is then an
abatement in the symptoms, and recovery is rapid.

Commonly, however, on account of the non-vascularity of the structure of the
tendon, the necrotic spot in it tends to spread. The wound is thus led to become
fistulous in character, and the pus forming within it prevented from escaping from
the original opening. As a result, lameness and fever persist. There is a gradual
increase in the severity of the symptoms, and later fistulous openings appear in the
hollow of the heel.

(d) Puncture of the Navicular Bursa.—This results from a prick
in exactly the same position as that last described, and means that the penetrating
object has gone deeper, It may be distinguished from puncture of the plantar
aponeurosis alone by the fact that there is an excessive discharge of synovia from
the wound. This, as it escapes, is at first clear and straw-coloured. Later it
becomes cloudy and flaked with pus, and shows a tendency to coagulate in yellowish
clots.

Pain and accompanying fever is most marked, much more so than when the plantar
aponeurosis alone is injured.

Should the original wound be insufficiently enlarged, or should its opening become
occluded by the solid matters of the discharge, then this condition, like the last,
ends in the formation of fistulous openings in the heel. These make their appearance
as hot, painful, and fluctuating swellings in that position. Later they break,
discharge their contents, and leave a fistulous track behind.

(e) Fracture of the Navicular Bone.—Penetration of the
substance of the navicular bone, without its fracture, adds nothing to the
symptoms we have described under puncture of the bursa. That the bone has been
reached by the penetrating object may be detected by probing. This, however, must be
performed with care, especially if a flow of synovia is absent. Otherwise, the wound,
as yet, perhaps, superficial enough to avoid penetrating even the bursa, is made a
penetrating one by the probe itself.

Fracture of the navicular bone is fortunately rare.

(f) Penetration of the Pedal Articulation and Arthritis.—This
we shall consider in greater detail in Chapter XII. It is sufficient here to state
that the condition may be suspected when a hot and painful swelling of the whole
coronet makes its appearance. There is at the same time a diffused oedema of the
fetlock and the region of the cannon, sometimes extending upwards to the whole of the
limb.

Of all the complications to be met with in punctured foot this is the one most to
be dreaded. The intense pain and the high fever render the animal weak and thin in
the extreme. The appetite becomes impaired, sometimes altogether lost, and the
patient in many cases appears to die from sheer exhaustion. Added to this is always
the extreme probability of the wound becoming purulent, and later the dread of
general septic infection of the blood-stream ensuing, and death resulting from that.
Even with the happier ending of resolution, anchylosis of the joint and incurable
lameness is more often than not left behind. (See Suppurative or Purulent Arthritis,
Chapter XII.)

(g) Ostitis and Caries of the Os Pedis.—Injuries to the os
pedis are met with in the anterior zone of the foot. Evidence that the bone has been
injured is not usually forthcoming until after the lapse of some days. One is led to
suspect it by the fact that there is no indication of the suppurative process
extending further upwards, coupled with the facts that great pain, high fever, and
extreme lameness persist, and that there is a continuous discharge from the wound of
a copious blood-stained and foetid pus. Used now, the probe reveals the fact that the
bone is bared, and conveys to the hand that is holding it a sensation of crumbling
fragility.

(h) Wounding of the Lateral Cartilage and Quittor.—This occurs
as the result of a deep stab in the posterior zone. Ordinarily, wounds in this
position are unattended with serious consequences, and the prick has to be a deep and
a severe one before the cartilage is reached. What then happens is that a spot of
necrosis is formed round the seat of puncture in the cartilage. This, unless met with
surgical interference, is sufficient to maintain the wound in a septic condition; it
takes on a fistulous character, and a quittor is formed. (See Chapter X.)

(i) Septic Infection of the Limb.—This we have already once or
twice referred to. It simply means that the septic matters from the wound have gained
the lymphatics, and finally the blood-vessels of the limb, and set up local lesions
elsewhere than in the foot. Although dismissed here with these few words, the
condition is a most serious one. Usually, it has resulted from penetration of the
pedal articulation and septic infection of the joint. In the vast majority of these
cases slaughter is both humane and economical.

Prognosis.—The first consideration in giving a prognosis in punctured
foot should be the position of the wound. When occurring in the middle zone, the
surgeon’s statements should be most guarded, and the dangers attending a wound in
that particular position fully explained to the owner. A wound in the anterior
position is, as we have said, far less serious, and one in the posterior region of
the foot even less serious still.

Whenever possible, the nail or other object causing the prick should be examined.
Much of the prognosis may be based upon the estimated depth of the wound, and this,
in many cases, it is far safer to calculate from the length of the offending body
than from the use of the probe. We need hardly say that in the middle zone the deeper
the prick, the more serious the case, and the less favourable the prognosis. As in
succession the sensitive sole, the plantar aponeurosis, the navicular bursa, the
navicular bone, or the pedal articulation is injured, so with each step deeper of the
prick is the severity of the case increased.

The shape of the penetrating object may also be considered. One excessively blunt,
and calculated to bruise and crush the tissues, will inflict a more serious wound
than one of equal length that is pointed and sharp.

The conformation of the foot should also be regarded. Wounds in well-shaped feet
are less serious than in feet with soles that are flat or convex, or in which the
horn is pumiced or otherwise deteriorated in quality.

Although unaffecting the prognosis so far as the actual termination of the case is
concerned, it may be mentioned that punctured foot is far more serious in a nag than
in a heavy draught animal. With an equal degree of lameness resulting in each case,
the former will be well-nigh useless, but the latter still capable of performing much
of his usual labour.

The temperament and condition of the patient will also in many cases largely
influence the prognosis. An animal of excitable and nervous disposition is far more
likely to succumb to the effects of pain and exhaustion than the horse of a more
lymphatic type. In the case of a patient suffering from a prick to a hind-foot while
heavily pregnant, the attempted forecast of the termination should be cautious. More
especially does this apply to the case of a heavy cart-mare. Ordinarily, the heavier
the breed, the greater the tendency to lymphatic swelling of the hind-limbs. With
pregnancy this tendency is enormously increased, and it is no uncommon thing to find
a cart-mare in this condition, with legs, as the owner terms it, ‘as thick as
gate-posts.’ A prick to the foot, with the lymphatics of the limb in this state, is
extremely likely to end in septic infection of the leg, for there appears to be no
doubt but that invasion of the lymphatics with septic matter is favoured by a
sluggish stream. Also, in the case of a patient in the advanced stages of pregnancy,
it must be remembered that, no matter how great may be the need, one is debarred, for
obvious reasons, from using the slings.

Treatment.—In a simple case—and by ‘simple’ here we mean
the case in which the injury is discovered early, and pus has not yet commenced to
form—our first duties are to give the wound free drainage, and to maintain it
in an aseptic condition. The first of these objects is to be arrived at by paring
down the horn in a funnel-shaped fashion over the seat of the prick. It is, perhaps,
even better to thin the horn down to the sensitive structures for some little
distance round the injury. By this latter method pressure from inflammatory exudate
is lessened, and the after-formation of pus, if unfortunate enough to occur, the more
readily detected, and the less likely to spread upwards. The matter of asepsis may
then be attended to.

When the puncture is sufficiently large to admit of it, the antiseptic dressing is
best applied by means of the probe. This instrument is thinly wrapped with tow, or
other absorbent material, so as to form a small swab. Dipped in a suitable solution
(as, for example, Zinc Chloride, Spts. Hydrarg. Perchlor., Carbolic Acid, or any
other that suggests itself), the swab is inserted into the prick, and the wound
conveniently mopped clean. A further portion of the medicated tow is then pushed
partially into the wound, and allowed to remain in position. The foot is subsequently
wrapped in a clean bag, and kept free from dirt. This dressing should be repeated
twice daily.

If the prick is in a dangerous position, and deep enough to occasion alarm, our
precautions to prevent the formation of septic matters within it may be more
elaborate. The thinning of the horn and the swabbing of the wound may, as before, be
proceeded with. In addition, the whole foot may then be immersed for some hours daily
in a cold bath, which bath should be strongly impregnated with one or other of the
following salts: Iron Sulphate, Zinc Sulphate, Copper Sulphate, Aluminium Sulphate,
Lead Acetate, or Sodium Chloride—better still, a mixture of the various
sulphates here mentioned. If preferred, one of the more commonly accepted
antiseptics—such as Carbolic Acid, Lysol, Boracic Acid, or Perchloride of
Mercury—may be substituted.

By the cold of the bath inflammatory phenomena are held in check, while its added
antiseptic prevents the formation of septic discharges. The lameness gradually
diminishes, and resolution is rapid. In this way deep and serious, wounds are
sometimes easily and successfully treated.

When suppuration has occurred—and this, by-the-by, is by far the most
frequent condition in which we find punctured foot—treatment must be prompt and
decided. Careful search must at once be made by thinning down the sole, and carefully
trimming the frog. On no account should the veterinary attendant rest content with
‘digging’ in one place, and upon that basing a negative opinion as to the existence
of pus. The paring should be carried on, until either pus or hæmorrhage shows
itself, in at least three positions—namely, at the most anterior portion of the
sole, and in the sole at each side of the frog. In addition to this, the frog itself
should be minutely examined for evidence of puncture, or for leaking of pus at the
spot where the horn of the heels joins the skin.

In many of our cases, however, this careful search is not so necessary. The
accompanying symptoms are so decided as to leave no doubt as to the condition of the
case. In such instances paring may often be commenced over the exact position of
suppuration as previously ascertained by percussion.

When met with, the track formed by the suppurative process should be followed up
in whichever direction it has spread. This will often necessitate the removal of the
greater part, if not the whole, of the horny sole.

Having given vent to the pus, and opened up the cavity made by its formation, the
foot should be placed in a hot poultice or, preferably, in a hot antiseptic
bath.[A]

[Footnote A: At the time of writing this, a certain amount of discussion is going
on in our veterinary journals as to whether a hot or a cold bath is the one
indicated. It is urged against the application of heat that it favours organismal
growth and reproduction, and tends rather to induce the spread of the suppurative
process than to overcome it. Those who hold this opinion urge in support of it that
cold applications are inimical to the life of the pus organism. At the same time, it
must be remembered that in just so far as cold inhibits the growth of the invading
germ, so in just the same degree does it adversely influence the functions of the
tissues that are to fight against it. To our minds the question thus set up must
always remain more or less a moot-point, and while we fully agree that cold
undoubtedly checks the growth of septic material, we just as fully believe that
warmth serves to place the healthy surrounding structures in a far better condition
to maintain a vigorous phagocytosis against it. We thus continue to advise a hot
antiseptic poultice, or, better still, a bath.—THE AUTHOR.]

At the end of the third or fourth day the poultice or the bath may be
discontinued, and the opening in the sole dressed with any suitable astringent and
antiseptic.

The most serious complication arising from this method of treatment is one of
excessive granulation of the sensitive sole. This we find to be successfully held in
check by a daily application of undiluted Spts. Hydrarg. Perchlor. (Tuson). Should
the granulations become very exuberant, then the knife must be called to our aid, and
the wound so made afterwards dressed with an astringent.

When the suppuration has under-run the horny frog there should be no hesitation in
at once removing all the horn that is visibly separated from the sensitive structures
beneath.

When the os pedis is splintered and carious, a portion of the sole round
the wound is removed, and the bone exposed. The diseased portion is scraped away
either with a curette or with the point of the drawing-knife. In this case the only
after-treatment called for is the application of suitable antiseptic dressings.

When necrosis of the plantar aponeurosis has occurred. We have already
pointed out the tendency there is in this case for the wound to maintain a fistulous
character, and lead to the formation of abscesses in the hollow of the heel. With a
wound in this position, as with a wound in any other, the only method of avoiding
this termination consists in removing all that is visibly diseased, whether it be
soft structures, bone, ligament, or tendon, and giving the wound free drainage.

This can only be done by removing the horny sole and frog, and cutting boldly down
upon the structures beneath. The operation is known as resection of the plantar
aponeurosis, or the complete operation for gathered nail.

Practised for some years on the Continent, this operation, on account of its
gravity, has been avoided by English veterinarians. From reported cases, however, it
appears often to be followed by success. That there is a large element of risk in the
operation is quite evident, if only from the two facts mentioned beneath:

1. That the close attachment of the plantar aponeurosis to the navicular bursa,
and the nearness of both to the pedal articulation, render penetration of a synovial
sac or a joint cavity extremely likely.

2. That there is always great difficulty in maintaining strict asepsis of the
foot, more especially if it is a hind one.

On the other hand, it may be argued that equal risk to the patient is run in
allowing him to remain with a disease (and that disease a progressive one) of the
structures so closely antiguous to the navicular bursa and the pedal
articulation.

If only for that reason we give the operation brief mention here.

The animal is prepared in the usual way for the operating bed; the foot soaked for
a day or two previously in a strong antiseptic solution, the patient cast and
chloroformed, and the operation proceeded with.

FIG. 106.—’CURETTE,’ OR VOLKMANN’S SPOON.

An Esmarch’s bandage should be first applied, and a tourniquet afterwards placed
higher up on the limb. The foot is then secured as described in an earlier chapter,
and the whole of the horny structures of the lower surface of the foot (the sole, the
frog, and the bars) pared until quite near the sensitive structures, or, if under-run
with pus, stripped off entirely. An incision is then made in each lateral lacuna of
the frog, the two meeting at the frog’s point. Each incision thus made should be
carried deep enough to cut through the substance of the plantar cushion. A tape is
then passed through the point of the frog, tied in a loop, and given to an assistant
to draw backwards. The plantar cushion itself is then incised in a direction from
before backwards, and pulled on by the assistant, so as to expose the plantar
aponeurosis.

Should this be found at all necrotic, it may be taken that purulent inflammation
of the navicular bursa and of the navicular bone itself exists. The operator must
then proceed to resection of the tendon in order to treat the deeper structures thus
affected. At its point of insertion into the semilunar crest the tendon is severed
and afterwards reflected. This exposes the inferior face of the navicular bone.
Instead of the glistening and clear appearance it ordinarily presents, its glenoid
cartilage is found to be showing hæmorrhagic or even purulent spots of
necrosis. The terminal portion of the tendon must then be excised.

To effect this a clean transverse incision is made at the extreme upper border of
the navicular bone. Here we are in close contact with the pedal articulation, and
great care is necessary in making this last incision, in order that the synovial sac
may not be penetrated.

All structures showing spots of necrosis should now be carefully removed, either
with the knife or with the curette. The knives most suitable for the last stages of
this operation are those depicted in Fig. 45 (c, d, and e). The
curette, or Volkmann’s spoon, we show in Fig. 106.

FIG. 107.—RESECTION OF TERMINAL PORTION OF THE PERFORANS. The horny sole and
the horny frog stripped from off the sensitive structures. a, The plantar
cushion; b, b, the plantar aponeurosis, or terminal portion of perforans;
c, the navicular bone; d, interosseous ligaments of the pedal
articulation; e, e, semilunar crest of the os pedis; f, inferior
surface of os pedis; g, g, the sensitive laminæ of the bars; h,
h, bearing surface of the wall; i, i, the sensitive sole; k, the
sensitive frog.

When at all diseased the glenoidal surface of the navicular bone should be
curetted, even to the extent of the removal of the whole of the cartilage. A healthy,
granulating surface is thus insured.

The above figure from Gutenacker’s ‘Hufkrankheiten’ explains shortly the position
of the operation wound and the structures involved, rendering further description
unnecessary here.

The operation ended, the dressing follows. Upon this depends very largely the
ultimate recovery of the patient, for it is only by careful attention and suitable
dressings that effectual repair of the injured structures may be brought about.

A light shoe is first tacked on to the foot, and those portions of the horny sole
that have been allowed to remain dressed with Venice turpentine, tar, or other
thickly-adherent antiseptic.

The exposed soft tissues are then dressed with pledgets of tow[A] soaked in
alcohol and carbolic acid. This dressing must be allowed to remain in position, and
is kept there by means of a bandage, or the shoe with plates (Fig. 55) and a bandage
over it. No pressure is needed; consequently, the pledgets of tow must not be too
thick.

[Footnote A: When using tow in the form of a pad, it is well to remember that many
small balls of the material rolled lightly in the palm of the hand and afterwards
massed together are far better than one large pad of the tow taken without this
preparation. The irregularities of the wound are better fitted, and the whole
dressing easier remains in situ (H.C.R.).]

In the after-dressing of the wound careful attention must be paid to the
granulating surface. Where tending to become too vigorous in growth it should be held
in check by suitable caustic dressings. At the same time it must be remembered that
the granulating process of repair is always more rapid upon the plantar cushion and
fleshy sole than upon the bone, or upon tendinous or cartilaginous structures. As a
result of this we have a wound showing various aspects of cicatrization. Healthy
granulation may be profuse in one spot, while in another it may be checked either by
a flow of synovia from the still open bursa, or by fragments of bone or of tendon
still acting as foreign bodies in the wound. These latter may be readily detected by
their standing out as dark and uncovered spots in the healthy granulation around, and
should be at once removed.

The time that an operation wound of this description takes to heal—and that
without complication—is from one to two or three months. Continuation of pain
and intensity of lameness are not to be taken as indications of failure. The
reparative inflammation in the synovial membrane is quite sufficient to induce pain
severe enough to prevent the animal from placing his foot to the ground for some
weeks, even though the progress of the case, all unknown, may be all that is desired.
So long as a great amount of pain is absent, and so long as appetite remains and
swellings in the hollow of the heel fail to make their appearance, so long may the
progress of the case be deemed satisfactory.

Recorded Case of the Treatment.—A cart-horse, aged six years, was
sent to the Alfort School by a veterinary surgeon for having picked up a nail in the
hind-foot. Professor Cadiot, judging the necessity for the complete operation,
performed it on January 14, and spared the plantar cushion as much as possible. In
consequence of the plantar aponeurosis being extensively necrosed, it was advisable
to scrape the navicular bone and a part of the semilunar crest. The wound having been
washed with a 1 per cent. solution of perchloride of mercury, it was dusted with
iodoform and packed with gauze, and covered with a cotton-wool dressing, kept in
position by means of a suitable shoe.

On January 16 there was no snatching up of the limb when the horse was made to put
weight upon it; he ate his food well, and his condition improved every day. On
January 21 the dressing was removed; the wound appeared pinky and granular, and there
was no suppuration. The clot remaining from the hæmorrhage after the operation
was removed, the wound was irrigated with a hot solution of sublimate, and then
dusted with iodoform and covered with a dressing of iodoform gauze and absorbent
wool. At this date the horse could stand on the injured limb. On January 31 a second
dressing was made, and the animal almost walked sound. On February 7 the wound had
almost closed up, save in its central part, where there was a small cavity, and the
lameness had disappeared. On February 15 the wound had completely healed, and its
borders were covered by a layer of thin horn. As the animal was sound it was sent to
work.

The author directs attention to the rapidity with which a large and complete wound
cicatrizes after the operation for gathered nail.[A]

[Footnote A: Veterinary Record, vol. XV., p. 226 (Jourdan).]

In the case of Penetrated Navicular Bursa, unaccompanied by the formation
of any large quantity of pus, and uncomplicated by necrosis of the aponeurosis, our
aim must be to maintain the wound in that happy condition. This is doubtless best
done by keeping the foot continually in a cold bath, rendered strongly antiseptic by
the addition of sulphate of copper and perchloride of mercury. Should there be
intervals when the bath must be neglected, the foot in the meantime must be kept
clean by antiseptic packing and bandaging, and a clean bag over all. This treatment
should be continued so long as the character of the discharge denotes that synovia is
running. If, in spite of our precautions, the discharge becomes purulent, then the
track made by the penetrating object should be syringed twice daily with a 1 in 1,000
solution of perchloride of mercury.

During the treatment it will be wise to shoe the animal with a high-heeled shoe.
We do not know as yet the full extent of the injury. The navicular bone may be
tending to caries; or necrosis of the plantar aponeurosis, all unknown, gradually
becoming pronounced. This calls for a relief of tension on the perforans, and is only
to be brought about by the high-heeled shoe.

The result of the inflammatory changes in the tendon, aided possibly by the use of
the high-heeled shoe, is to afterwards bring about contraction. Where this has
occurred, and the animal walks continuously on his toe, the shoe with the projecting
toe-piece (Fig. 84) must be applied. When the continual use of the toe-piece appears
inadvisable, the shoe devised by Colonel Nunn may be used in its stead (see Fig.
108).

The toe-piece is screwed into the toe of the shoe when the horse is about to be
exercised, and forms a powerful point of leverage with which to stretch the
contracted tendon, and the shoe, being thin at the heels, admits of this. The
advantage of this form of toe-piece over the ordinary form of fixed toe-lever is that
it can be removed when the horse is in the stable; while the curved point diminishes
the danger of the horse hurting itself—a danger always present if it is on a
hind-foot. (See also Treatment of Purulent Arthritis in Chapter XII.)

FIG. 108.—COLONEL NUNN’S SHOE WITH DETACHABLE TOE EXTENSION.

Should a Sinuous Wound remain in the region of the Lateral Cartilage, it
should be explored, and its depth and likely number of branches ascertained. Should
this exploration denote that the cartilage itself is diseased, or that the wound is
not able to be sufficiently drained from the sole, then we know that we have on our
hands a case of quittor. The treatment necessary in such a case will be found
described in Chapter X.

When the Complication of Purulent Arthritis has arisen, the surgeon has to
admit to himself, reluctantly no doubt, that the case is often beyond hope of aid
from him. Nothing can be done save to order continuous antiseptic baths and
antiseptic irrigation of the wounds with a quittor syringe, and to attend to the
general health and condition of the patient. At the best it is but a sorry look-out
both for the veterinary attendant and the owner of the animal. Even with resolution
incurable lameness results, and the animal is afterwards more or less a walking
exhibition of the limitations of surgery, while the owner, unless the animal is
valuable for the purpose of breeding, finds himself encumbered with a life that is
practically useless. (See Treatment of Purulent Arthritis, Chapter XII.)

In the case of Lameness Persisting after the healing of all appreciable
lesions, then neurectomy is followed by good results. The animal, apparently
recovered, is for a long time useless. Lameness persists for several months, as if
the nail had at the moment of its penetration caused lesions, which doubtless it
sometimes does, similar to those of navicular disease. Examination of the foot in
this case reveals no lesion, and the pain has evidently a deep origin. The lameness
caused by it is subject to variation. Frequently it becomes lessened during rest, and
increased by hard work, while sometimes it is very much more pronounced at starting
than after exercise.

It is here that neurectomy is called for. The operation does nothing to impede the
work of healing going on, and allows free movement of the foot and pastern to take
place. At the same time suffering and emaciation cease, and the animal is rendered
workable.[A]

[Footnote A: Veterinary Record, vol. ii., p. 371.]

C. CORONITIS (SIMPLE). TREAD, OVERREACH, ETC.

1. Acute.

Definition.—Under the heading of simple coronitis in its acute form
we intend to describe those inflammatory conditions of the skin and underlying
structures of the coronet occurring without specific cause. Specific coronitis will
be found described in Chapter IX.

Causes.—This condition is almost invariably set up by an
injury—either a bruise or an actual wound—to the coronet. By far the most
common among such injuries are those inflicted by the animal himself by means of the
shoes.

That known as ‘tread’ is caused by the shoe on the opposite foot, and may happen
in a variety of ways. More often than not it is met with in the feet of heavy draught
animals, and is there caused by the calkin, either when being violently backed or
suddenly turned round. It may also occur in horses with itchy legs, as a result of
the animal rubbing the leg with the shoe of the opposite limb. The irritation in this
case is nearly always due to parasitic infection (Symbiotes equi), and becomes
sometimes so unbearable as to render the animal unmindful of the injury he may be
inflicting so long as he experiences the relief obtained by the rubbing.

Self-inflicted tread is also sometimes met with when horses are worked abreast at
plough. The animal in the furrow, with one foot sometimes in and sometimes out of the
hollow, is caused to make a false step, and so brings the injury about.

Animals worked in pairs are further liable to receive a tread from the foot of
their companion. This is commonly seen in heavy animals at agricultural labour in
fields, where the walking is uneven, and abrupt turning constant. It is not uncommon
either in animals at work in vans in town, and is occasionally met with in the feet
of carriage-horses.

‘Overreach’ is the term used to indicate the injury inflicted on the coronary
portion of the heel of the fore-foot by the shoe of the hind. Ordinarily, overreach
occurs when the animal is at a gallop, and is thus met with in its severest form in
hunters and steeplechasers. It can only occur when the fore-foot is raised from the
ground and the hind-foot of the same side reached right forward. When the feet
separate the injury takes place. In its movement backwards the inner border of the
shoe of the hind-foot catches the coronet of the fore, and tears it backwards with
it. Quite frequently a portion of the skin is removed entirely, but often it hangs as
a triangular flap. The flap in such a case is always attached by its hindermost edge,
and indicates plainly enough that the direction of the blow that cut it must have
been from before backwards.

Although ordinarily inflicted at the gallop, the same injury may, nevertheless, be
caused by allowing a fast trotter, and one with extreme freedom of action behind, to
push forward at the utmost limit of his pace. The outside heel is the one most
subject to the injury.

While the common form of injury to the coronet is, as we have described, that
occasioned by the animal’s own shoe, or that of a companion, it is evident that the
foot is also open to similar injuries from quite outside sources. Falls of the shafts
when unyoking animals from a heavy cart, blows or wounds from the stable fork, wounds
resulting from the foot becoming fixed in a gate or a fence, either may equally well
set up the mischief.

Apart from severe injury, a particularly troublesome form of coronitis may arise
from the condition of the roads. We refer to the conditions attendant on a thaw after
snow. The animal is called upon to labour in, or perhaps stand for long periods in, a
mixture of snow and water, or snow and mud. That this must have a prejudicial effect
upon the structure of the coronet is plain. The circulation of the part, already
predisposed to sluggishness by reason of its distance from the heart, is farther
impeded by the action of the cold. Small abrasions of the skin, so small as to scarce
be noticeable, are in this case freely open to infection with the septic matter the
mud contains. Necrosis and consequent sloughing of the skin is bound to follow, and
an extensive ulcerous wound, or a spreading suppuration of the coronary cushion is
the result.

Symptoms.—We will take first the case in which no actual wound is
observable. Here the first indication of the trouble is the appearance of an
inflammatory swelling, confined usually to one side, but extending sometimes to the
whole of the coronet. Always the part is hot and tender, and with it the patient is
lame—so much so, in many cases, as to be unable to put the foot to the ground,
the toe alone being used.

In a mild case, uncomplicated by septic infection, these symptoms rapidly subside,
and resolution occurs.

Always, however, the presence of septic infection must be suspected and looked
for. When this has occurred, the inflammatory swelling becomes larger and more
diffuse, and the animal fevered. This is then followed by a slough of the injured
part. A portion of the skin first becomes gray, or even black, in appearance, and
around it oozes an inflammatory exudate, or even pus. The skin immediately adjoining
the spot of necrosis is swollen and hyperæmic, and extremely painful and
sensitive. Later, the necrosed portion becomes cast off, and an open wound remains.
This as a rule marks the turning-point in the case. The pain and other symptoms
rapidly abate, and the wound, with proper attention, is not more than ordinarily
difficult to treat.

In the case of an actual wound the symptoms are probably less severe. The injury
is, in this instance, the sooner detected, and remedial measures put into operation.
In this manner the formation of septic material is often checked, and nothing but the
treatment of a simple wound demands attention.

There are, however, complications.

Complications—(a) Diffuse Purulent Inflammation of the Sub-coronary
Tissue.—This condition is brought about by the spread into the loose tissue
of the coronary cushion of the septic material introduced by the tread. The whole
coronet in this instance becomes excessively swollen, hot, and painful, and the
dangerous nature of the complication is evident enough when the structure and
situation of the parts involved is considered. The amount of tendinous and
ligamentous material in the neighbourhood offers a strong predisposition to necrosis,
and the necrosis, with its attendant formation of pus, offers a further danger when
the close proximity of the pedal articulation and the unyielding character of the
horny box is considered with it.

The pus formed in this condition may remain confined to the coronet and break
through the skin as an ordinary abscess, or it may, before so doing, burrow beneath
the wall, and invade the sensitive laminæ. In this case, whenever portions of
the secreting layer of the keratogenous membrane are destroyed, or perhaps only
temporarily prevented from fulfilling their horn-producing functions, then
corresponding cavities in the horn are the result (see Fig. 109).

(b) Purulent Arthritis.—Only too readily the pus so formed tends to
penetration of the articulation and the causation of an incurable arthritis (see
Chapter XII.).

FIG. 109.—MESIAL SECTION OF A HOOF ILLUSTRATING THE CONDITIONS FOLLOWING
UPON CORONITIS. a, Cavity in the horn of the wall; b, enlargement of
the coronet and the horn of the wall following sub-coronary suppuration; c,
cavity in the wall following purulent inflammation of the sensitive laminæ;
d, hollow in the horn of the sole consequent upon suppuration of the sensitive
sole.

(c) Necrosis of the Extensor Pedis.—This may arise either as a result
of spreading purulent infection of the coronary cushion, or as a result of direct
injury immediately over it. The close relation of the terminal portion of this tendon
with the pedal articulation, and the incomplete protection from outside injuries here
afforded to the joint by the horny box, sufficiently points out the gravity of the
condition.

(d) Penetration of the Articulation.—This also may be a result either
of the inroads made by pus, or of an actual wound. When occurring from the latter, it
is seen more often than not in the hind-foot, being there caused by the calkin of the
opposite foot. Where a wound in this position is characterized by an excessive flow
of synovia, the condition should be suspected, and, if the wound be large enough, the
little finger should be introduced in order to ascertain. Needless to say, the injury
is a grave one.

(e) Sand-crack.—Sand-crack is likely to result from tread when an
injury is inflicted in the region of the quarter by a severe overreach. Treads, too,
especially with the calkin of the hind-shoe, are especially apt to end in this way.
In this latter instance the sand-crack usually has its origin in a nasty jagged tear
at the top of the wall of the toe.

(f) Quittor.—In one respect any suppurating wound at the coronet may
be deemed a quittor. By indicating quittor as a complication of coronitis, however,
we denote the more serious form of this disease, in which the wound has taken on a
sinuous character, and conducted pus to invasion of the lateral cartilage. It is one
of the worst complications we are likely to meet with in this condition, and will be
found fully described in Chapter X.

(g) False Quarter.—This complication of coronitis occurs when the
injury or after-effect of the formation of pus has been severe enough to destroy
outright a comparatively large portion of the papillary layer of the coronary
cushion. To this condition we devote Section D of this chapter.

Prognosis.—In giving a prognosis in a case of coronitis, attention
should be paid to the manner in which the condition originated, and the extent, when
present, of the wound.

When the inflammatory swelling has arisen from bruising alone, without actual
division of the skin, when the weather is that of winter, and the swelling showing a
marked tendency to spread, then the prognosis must be guarded. As we have seen, this
state of affairs is probably ushering in a condition of spreading suppuration of the
coronary cushion, and considerable gangrene and sloughing of the skin. We have here
no intimation as yet of how far the suppurative process may run, nor what important
structures it may involve. Consequently, the guarded prognosis we have mentioned is
imperative.

Where an actual wound is to be seen, and where advice is sought early, then a more
favourable opinion may be advanced. In this case antiseptic measures, commenced early
and persisted in, may prevent the rise of further mischief.

It goes without saying that, should there arise any other of the complications we
have mentioned (viz., Arthritis, Necrosis of the Extensor Pedis, Sand-crack, Quittor,
and False Quarter), the fact should be pointed out to the owner, and the prognosis
regulated thereby.

Treatment—Preventive.—Seeing that at any rate the majority of
cases of coronitis result from injuries inflicted by the shoes, we may look at once
to that particular for a means of prevention.

Take first the case of ‘treads’. There is no doubt that they are most common in
animals shod with heavy shoes and with high and sharp calkins. This suggests at once
that a preventive is to be found in substituting a calkin that is low and square.

Where the injury is an overreach, and where, on account of the animal’s pace and
manner of gait it is in risk of being constantly inflicted, the shoeing should be
seen to at once.

We have already pointed out that it is the inner border of the lower surface of
the toe of the hind-shoe which, in the act of being drawn backwards, inflicts the
injury. (See Fig. 110).

In this case prevention may be brought about either by shoeing with a shoe whose
ground surface is wholly concave, or by bevelling off the sharp border (see Fig. 110,
a, p. 236). When the tendency to overreach is not excessive, prevention may in
many cases be effected by simply placing the shoe of the hind-foot a trifle further
backwards than would ordinarily be correct, thus allowing the horn of the toe to
project beyond the shoe. This at the same time does away with the annoyance of
‘forging’ or ‘clacking,’ which, as a rule, accompanies this condition.

While recognising the value of shoeing in these cases, we must not forget that a
great deal may be brought about by careful horsemanship. The animal should be held
together and kept well up to the bit, but should not be allowed to push
forward at the top of his pace. With many animals of fast pace and free action
overreach is more an indiscretion of youth than any defect in action or conformation,
and his powers should therefore be husbanded by the driver until the animal has
settled down into a convenient and steady manner of going.

FIG. 110.—UNDER SURFACE OF THE TOE OF A HIND-SHOE. a, Marks the
portion of the inner margin that inflicts overreach.

FIG. 111.—THE INNER MARGIN OF THE INFERIOR SURFACE OF THE HIND-SHOE BEVELLED
TO PREVENT OVERREACH.

Curative.—Although in some cases it is so small as to go undetected,
we may take it that in all cases of coronitis there is a wound, with consequent
danger of septic infection of the surrounding parts. Therefore, after attention to
the shoeing and removal of the cause, the first indication in the treatment will be
to render the parts aseptic. This is best done by removing the hair from the coronet
and soaking the whole foot in a cold antiseptic solution. After removal from the
bath, the coronet may be dressed with a moderately strong solution of carbolic acid
or perchloride of mercury. When the injury is slight and recent, such is sufficient
to effect resolution.

When marked swelling persists, however, and the increase in heat and tenderness
denotes the formation of pus, recovery is not so easily obtained. In this case the
application of hot poultices or hot baths is called for. By these means suppuration
is promoted and induced to early break through in the most favourable
position—namely, the softened skin of the coronet. The pus so escaping is
always more or less blood-stained, and contains both large and small pieces of broken
down and decomposed tissue. After discharge of the pus, the cavity remaining should
be mopped out with an antiseptic solution, and a pledget of antiseptic tow or other
material left in position. All that is then needed is constant dressing in a suitable
manner. We prefer in this instance washing some three or four times a day with hot
water until a perfectly clean wound is obtained, and, after the washing, painting the
raw surface with a strong solution (1 in 200, or 1 in 100) of perchloride of
mercury.