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.
[Illustration: 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.
[Illustration: 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).
[Illustration: 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_.
[Illustration: 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.
(_a_) THE BRITTLE HOOF.
_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.
[Illustration: 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).
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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).
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: FIG. 91.---THE BEARING 'EASED' BY REMOVAL OF THE WALL.]
[Illustration: 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.
[Illustration: 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).
[Illustration: FIG. 94, FIG. 95, 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.
After 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.
[Illustration: FIG. 97. The dotted lines outline the V-shaped portion of
wall to be removed in the treatment of complicated toe-crack.]
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[ILLUSTRATION: 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:
Subacetate of lead liquid ... ... ... 128 grammes.
Sulphate of zinc [=a=a] ... ... ... 64 grammes.
Sulphate of copper, [=a=a] ... ... ... 64 grammes.
Acetic acid ... ... ... ... 1/2 litre.
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.
[Illustration: FIG. 102.--THREE-QUARTER SHOE.]
[Illustration: 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.
[Illustration: FIG. 104.--SHOE WITH A 'DROPPED' HEEL.]
[Illustration: 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.