DEFECTS OF THE HOOF.
A. Changes of Form.
1. THE FLAT AND THE FULL HOOF (DROPPED SOLE).
(_a_) _Flat Hoof._—A flat hoof is one whose toe and side walls are
_inclined very obliquely_ to the ground-surface, and whose sole is _on
a level_ with the bearing-surface of the wall.
It exists most often in horses bred in low-lying, marshy countries.
Frequently the frog is well developed, and projects considerably beyond
the level of the wall. The branches of the sole sink perceptibly under
the weight of the body, much more than in better-formed hoofs.
[Illustration: FIG. 200.
Cross-section of a shod flat foot: _a_, sufficiently high
bearing-edge of wall, and a horizontal bearing-surface on the shoe;
_b_, insufficient height of bearing-edge of wall, and therefore a
corresponding downward and inward inclination of the bearing-surface of
the shoe.]
_Preparing the Hoof for the Shoe._—The rule is to =spare= the plantar
surface of the foot. After removing from the sole what little loose
horn there may be, level the usually deficient bearing-surface of the
wall with the rasp. The outer border of the wall, especially at the
toe, should be rounded off rather more strongly than usual, because the
toe requires and will bear considerable shortening. Outward bendings of
the lower border of the wall should be removed as far as it is
practicable to do so.
The shoe, which should be rather wider in the web and thicker than
usual, should have its bearing-surface shaped to correspond to the
bearing-surface of the wall; that is, if the bearing-surface of the
wall is below the margin of the sole (the sole of the foot being
uppermost), then the bearing-surface of the shoe should incline
downward and inward (Fig. 200, _b_). The bearing-surface of the
branches, however, must always remain horizontal. The shoe always
requires deep concaving, especially along the inner branch of the sole.
If the quarters are weak, the walls defective, or there are corns,
cracks, loose walls, or other diseases of the hoof, a =bar-shoe= should
be selected.
(_b_) _Full Hoof_ (Dropped Sole).—A full hoof is one whose sole instead
of being concave is convex,—that is, bulges beyond the bearing-surface
of the wall. It either arises gradually from a flat hoof or is the
result of laminitis (founder). In full hoofs the lower surface of the
os pedis is of the same shape as the horny sole.
_The preparation of a full hoof_ for the shoe consists merely in
removing all loose horn. In case the dropping of the sole is very
pronounced, the bearing-surface of the wall should be built up
artificially with Defay’s hoof cement. The shoe should be light, but
broad in the web, and furnished with a more or less deep concaving,
which extends from the inner edge of the web to the outer edge of the
shoe, and corresponds in shape to the bulging of the sole. By reason of
the deficiency of the wall, the =bar-shoe= deserves the preference over
an open shoe. It is frequently necessary to apply toe- and heel-calks
to remove the hoof from contact with the ground. The nails should he
thinner and longer than usual, and a more secure position of the shoe
may be secured without injury to the hoof by drawing up two side-clips.
Flat and full hoofs are =incurable=. Shoeing is of benefit only in
rendering such horses serviceable. Soles that are soft and sensitive
should he smeared with crude turpentine or pine-tar, though unusual
sensitiveness calls for a leather sole. Horses with full hoofs
should not be driven faster than a walk over hard roads. During
long-continued spells of wet weather softening of these hoofs should
be prevented by smearing the soles with a hoof-ointment containing
resin.
2. THE UPRIGHT OR STUMPY HOOF.
The upright or stumpy hoof is that form in which the quarters, with
relation to the toe, are too long (too high). The wall at the toe
stands very steep, in some cases perpendicular, and is strongly worn
away by standing and travelling.
[Illustration: FIG. 201. Upright or stumpy hoof, shod with a “tip.”]
[Illustration: FIG. 202. Beaked shoe for stilt-foot.]
_Causes._—1. The upright hoof is peculiar to the “standing under”
position (Fig. 53, page 66) and to the so-called bear-foot (Fig. 70,
page 72).
2. It arises also as a result of all those alterations in the direction
of the limbs which tend to remove the quarters from contact with the
ground (contraction of the flexor tendons, spavin,—Fig. 202).
3. It may arise gradually from neglect of the hoofs of horses running
barefoot.
4. It may arise from excessive shortening of the toe in relation to the
quarters.
_Shoeing._—The forms of hoofs mentioned in class 1 should be left
as they are. The hoofs that fall under class 2 should be dressed
and shod until a more natural setting down of the foot is secured.
This is brought about by sparing the quarters, and applying a shoe
with thickened branches or with heel-calks. Where the service of the
animal is exacting and upon hard streets, the toes, especially of
the hind shoes, may be made more durable by welding in steel plates.
Besides, the shoe should be moderately _base-wide_ around the toe,—that
is, should be bevelled downward and outward, should have a _strong
toe-clip_, and should be _quite concave at the toe_ and _rolled_.
(Figs. 203 and 204). Should the hoof tip forward whenever the weight is
thrown upon the limb, a shoe with a spur projecting from the centre of
the toe, and turning back and pressing upon the wall just underneath
the coronary band, will be of service (Fig. 202).
[Illustration: FIG. 203.]
[Illustration: FIG. 204. Shoe for stumpy hoofs, viewed from
ground-surface, hoof-surface, and in profile.]
Only those upright hoofs which are the result of the causes mentioned
in 3 and 4 are to be dressed as ordinary hoofs, and if the service
required is not too exacting they should be shod with tips (Fig. 201),
or with shoes with thinned branches.
3. THE CONTRACTED HOOF.
_A hoof which has deviated from its normal form in such a manner that
its posterior half, either in part or as a whole, is too narrow, is
a contracted hoof._ The walls of the quarters assume an abnormally
oblique direction downward and inward towards the median line of the
hoof.
When contraction affects only one quarter, it is called _unilateral
contraction_, or abnormal wryness (Fig. 211).
[Illustration: FIG. 205.
A fore-hoof with bilateral contraction of the quarters: _a_, spur of
horn prolonged from the buttress, which compresses the frog; _b_,
narrow median lacuna of the frog.]
The buttresses are usually very much prolonged and press upon the frog
and cause it to shrink. The bars no longer run in the natural straight
direction from the point of the frog backward and outward, but describe
a circle passing outward, backward, and inward.
[Illustration: FIG. 206.
_A_, Defay’s shoe for expanding the quarters of a hoof; _a_, clip
apposed to the buttress; _b_, slot sawed at the toe to weaken the shoe;
_B_, screw for expanding the Defay’s shoe.]
Contraction affects front feet, especially those of the _acute-angled_
form, more often than hind feet. In order to determine whether or not a
hoof is too narrow, we should always examine the frog and its lateral
lacunæ. If the frog is small and narrow, and the lateral lacunæ very
narrow and deep, there can be no doubt but that the hoof is too narrow
(contracted).
_The causes_, aside from too little exercise, are chiefly errors in
shoeing, such as weakening the posterior half of the hoof, leaving
too long a toe, either neglecting to remove the spurs of horn which
grow from the buttresses and press upon the frog, or removing them
incompletely, and using shoes whose branches are either _too wide
apart_ or are inclined downward and inward, so that under the weight of
the body _the heels are squeezed together_ and contraction is favored.
_Prevention and Treatment._—First, it should be borne in mind _that
whatever exercises moderate pressure upon the sole, frog, and bars
tends to expand the hoof_. The action and value of the various shoes,
frog-, and sole-pads, are measured by this rule. For this reason a
shoe with heel-calks is never advisable if an open flat shoe without
other means of relief can be used. Furthermore, since contraction is
the parent of nearly all diseases of the hoof (corns, quarter-cracks,
bar-cracks, thrush of the frog), we should use the greatest care to
=prevent= it by dressing the hoof as described on pages 98 to 103,
using flat shoes with a =horizontal bearing-surface for the quarters=,
giving =abundant exercise, preventing drying out of the horn=, and
allowing the animal to go barefoot whenever possible. _Where the
contraction is but slight_ the foregoing rules will be found sufficient.
_In very pronounced contraction, where the hoof is not acute-angled,
an expansive shoe_ with clips raised at the ends of the branches to
press against the buttresses may prove very advantageous; but under
no conditions should violence be used in expanding the heels with the
expanding-screw. This is an act of extreme delicacy, and should be
performed only by experienced veterinarians.
_In very pronounced contraction of one or both quarters of hoofs of
every degree of obliquity_ we may obtain a continuous expansive action
by the use of one of the numerous V-shaped springs, of which the
_Chadwick spring_ is the best (Fig. 207 and 208). After levelling the
wall and thinning the branches of the sole, the points of the spring
are set against the =buttresses=, the apex of the spring moved to
and fro till the points have bored well into the horn, when the apex
is laid against the sole at the toe, the sole filled with tar and
oakum and covered by a leather sole, and a bar-shoe applied. If the
contraction be less pronounced, or if the frog be much shrunken we may
place a Chadwick spring beneath a rubber bar-pad with a short shoe. The
spring may be stiffened from shoeing to shoeing, first by introducing
the ferrule at the apex of the spring and later by shifting the ferrule
toward the shoulder (Figs. 207, _b_, and 208, _b_).
[Illustration: FIG. 207.
The Chadwick spring for expanding contracted quarters: _a_, apex of
spring; _b_, ferrule to stiffen the spring; _c_, point which is buried
in a buttress of the hoof.]
[Illustration: FIG. 208.
A fore-hoof showing a Chadwick spring in proper position: _a_, Chadwick
spring; _b_, ferrule to stiffen spring as desired; _c_, uncompressed
spring before it has been engaged against the buttresses; _d_,
buttresses in which points of spring are buried.]
For contracted hoofs of the _acute-angled form_ we use the bar-shoe,
and if there are other diseases of the hoof present, or if we wish a
more rapid and continuous expansive action, we use also a leather sole
with foot-packing with or without a buttress spring. A foul frog should
be properly cleansed, and then disinfected with pine-tar thinned with
alcohol or crude wood-vinegar (pyroligneous acid).
Further curative measures are: turning the horse out without shoes
(expensive and seldom practicable); applying tips; using shoes the
bearing-surface of whose branches inclines downward and outward
(unilateral contraction requires but one branch to be so constructed);
hoof-pads of rubber (Figs. 145, 146, and 147), straw, rope, cork,
hoof cement, etc. Special forms of contraction are distinguished, and
are as follows:
(_a_) _The Contraction of Wide Hoofs._—This contraction is manifest
as a concavity or groove in the wall just below the coronet, usually
at the quarters, though sometimes extending entirely around the foot
parallel to the coronary band (Fig. 209). Pain is produced in the
contracted area by lightly tapping the horn, but not by moderate
pressure with the hoof-testers.
[Illustration: FIG. 209.
Wide fore-hoof with “coronary contraction”: (_a_) broad shallow groove
in each quarter, and disappearing toward the toe.]
Green horses with wide hoofs, just from the pasture, are particularly
liable to this form of contraction. As a rule, the lameness does not
disappear completely until the wall has assumed its natural, straight
direction by growing down properly from the coronary band.
In dressing the hoof and applying the _bar-shoe_, care must be taken
that the lower border of the wall underneath the painful area is
lowered so much that it will not receive direct pressure from the shoe.
(_b_) _Contraction of the Sole._—This is accompanied by an unnatural
direction of the wall. Instead of the wall being straight from the
coronet to the shoe, it describes a curve whose convexity is outward
(keg-shaped, claw-shaped when seen from the side) (Fig. 210). The hoof
seems constricted (tied in) at the coronet and at its plantar border,
the sole is abnormally concave (arched), and the plantar surface of
the hoof is considerably shortened from toe to heel. It happens in
both shod and unshod horses, with otherwise strong hoofs, but is quite
rare. It is occasionally associated with navicular bursitis (“navicular
disease”).
_Causes._—Principally dryness, too little exercise, and shoes without
horizontal bearing-surface.
[Illustration: FIG. 210.
A fore-hoof with a contracted sole, properly shod: _a_, toe convex
in profile; _b_, shoe fitted full all around, and “bearing-surface”
inclining outward; _c_, outer border bevelled base-wide.]
The treatment is correspondingly simple: The shoes should be flat,
fitted full all around to coax the wall out at every point, and the
outer border bevelled base-wide, so as to furnish a base of support
that is wider and longer than the hoof. In moderate contraction of the
sole, the bearing-surface of the shoe should be perfectly horizontal,
but if the contraction be very pronounced, the entire bearing-surface
should incline downward and outward (even at the toe). No toe-or
side-clip should be used. The shoe should be reset every two weeks; the
sole kept so thin by paring that it will spring under thumb pressure,
and kept moist by washing, tubbing or “stopping,” and the animal given
moderate exercise daily.
_In all forms of contraction of the hoof abundant exercise and the
maintenance of the natural pliancy of the horn by daily moistening
(washing) with water are absolutely necessary for successful treatment._
4. THE WRY HOOF.
If one side wall and quarter is steep, and the other very slanting
or oblique, we term such a hoof a “wry hoof.” Such a hoof divided
in the middle line presents two very _dissimilar_ halves. There are
three classes of wry hoofs: 1, normal wry hoofs (see Figs. 63-66);
2, pathological wry hoofs, or hoofs contracted in one quarter (see
contracted hoofs); 3, wry hoofs which are the result of improper
shortening of the wall and of neglect in horses running barefoot.
Only the second and third classes of wry hoofs require especial
attention. First, the more oblique wall must be cut down, and the steep
wall spared,—a procedure which differs essentially from that employed
in treating the first class, but is, nevertheless, entirely warranted,
because these second and third kinds of wry hoofs do not correspond to
the direction of the limb.
[Illustration: FIG. 211.
A wry right front foot of the base-wide class, viewed from behind. The
bar-shoe is fitted full along the contracted inner quarter, and snug
on the outside. The inner branch of the frog rests upon the bar of the
shoe; the outer branch is free. The inner quarter from the last nail
back to the frog is free of the shoe.]
In order to take weight from the steep wall, we use with advantage
a _bar-shoe_, which should be longer and wider than the hoof on its
contracted side. In other words, enlarge the base of support by making
the branch of the shoe broader. If an entire side wall and quarter
is contracted the branch of the shoe beneath must be broad, the
border bevelled base-wide, and the branch punched so deeply that the
nail-holes will fall upon the white line.
In old work-horses any sort of shoe may be used, though a flat shoe
serves the purpose best. If a hoof is wry from faulty paring, and we
cannot at once completely restore the proper relative slant of the two
walls by paring alone, we may use a shoe with a thicker branch for the
half of the hoof which is too low (too steep).
In colts such wry hoofs can often be cured only by shoeing. The shoe
employed for this purpose is so made that the branch underneath the
steep (contracted) wall is quite thick, but gradually thins away around
the toe to the end of the other branch. In strongly marked cases the
thin branch may end at the middle of the side wall (a three-quarter
shoe). This method of shoeing shifts the body-weight upon the slanting
wall and restores the foot to its proper shape in from two to four
shoeings.
_Causes._—Unequal distribution of the weight in the inner and outer
halves of the foot, in conjunction with excessive cutting down or
wear of the steeper wall. All faults in shoeing which tend to produce
contraction of the heels aid in the formation of a wry foot, especially
when these faults directly affect the steep wall. Neglect of the colt’s
hoofs during the first years of life frequently lays the basis for wry
foot in later years. All wry feet are more susceptible to disease than
others.
The amount or degree of wryness varies considerably. In a moderately
developed case the steep wall (usually the inner) will be drawn in
at the plantar border of the quarter, presenting a convex surface
between this border and the coronet, and the adjacent branch of the
frog will be more or less shrunken. In extreme cases the slanting wall
(usually the outer) will also be involved and bent in the opposite
direction,—_i.e._, will be concave (dished) between coronet and lower
border (crooked hoof).
_Prognosis._—When the degree of wryness corresponds to the slant of the
foot-axis and the old shoe shows nearly uniform wear, the defect is not
directly injurious. In very pronounced “wryness,” however, with thin,
bent walls, a number of associated lesions, such as corns and cracks,
may be present and render the animal unfit for service upon paved or
macadam roads.
5. THE CROOKED HOOF.
A crooked hoof (Fig. 212) is one whose walls (viewed from in front or
behind) do not pass in a straight, natural direction from the coronet
to the ground, but are bent in such a manner that the bearing-surface
of the wall in relation to the foot-axis lies either too far out or in.
It may occur on any foot, but is seldom strongly marked.
_Causes._—The causes are either long-continued leaving of one-half of
the wall too high, or the use of shoes shaped for normal feet upon
hoofs of the base-wide position.
[Illustration: FIG. 212.
A crooked right fore-hoof of the base-wide position: _a_, convex wall,
too high; _b_, concave wall, too low; _c d_ shows how much of the outer
wall must be removed with the hoof-knife; _f_, superfluous horn to be
removed gradually with the rasp; _c e_ and _g h_ indicate the position
of the shoe with relation to the hoof.]
The principal part of the treatment is the proper dressing of the hoof.
The wall which is bent out at the middle and drawn in at the plantar
border is, as a rule, too high and too near the centre of the foot
(too narrow); the opposite wall, on the contrary, is too low and too
far from the centre of the foot (too wide). This explains the manner
in which the hoof should be cut down and rasped. The shoe must be laid
out as far as possible towards the side which is too high and narrow.
A straight edge placed against the high wall touches it only at its
middle. The distance of this line from the lower edge of the wall shows
us how far the surface of support—namely, the shoe—should be set out
beyond the horn. If the straight edge be placed against the opposite
wall, it will touch only at the coronet and at the plantar border,
showing that the wall is concave. The distance of the middle of this
wall from the straight edge shows us how much too wide this half of
the wall is at its plantar border, and how much of the outer surface
of the wall at its plantar border should be removed with the rasp.
The restoration of a crooked hoof to its normal form requires several
shoeings.
6. OSSIFICATION OF THE LATERAL CARTILAGE (SIDE-BONE).
The ossification of a lateral cartilage (Fig. 213) consists in a change
of the cartilage into bone. Heavy horses are more frequently affected
than lighter ones. It most often involves the outer cartilages of the
forefeet, seldom both cartilages. Side-bones always interfere with the
physiological movements of the foot, and may, indeed, entirely suppress
them.
[Illustration: FIG. 213.
A left fore os pedis viewed in profile, showing ossification of the
external lateral cartilage: _a_, dotted line shows normal line of
union of cartilage with wing of os pedis; _b_, ossified portion (“side
bone”). The unossified cartilage has been removed by maceration.]
The disease can only be diagnosed with certainty after the upper part
of the cartilage has ossified. The coronet is then rather prominent
(bulging), and feels hard. The gait is short, and cautious, and
well-marked lameness often follows severe work. As _causes_, may
be mentioned predisposition in heavy lymphatic horses, and violent
concussion or shock due to fast work upon hard roads. The disease is
_incurable_.
A special method of shoeing is only necessary when the outer cartilage
is ossified and the quarter upon that side is contracted. After
removing the old shoe, whose outer branch is, as a rule, more worn away
than the inner, the outer wall will always be found too high, due to
the fact that there has been little or no expansion and contraction
in this quarter and, therefore, little or no wear of the horn against
the shoe. The hoof is therefore wry,—on the outside too high, and on
the inside too low. This shows us how the foot should be dressed so
as to obtain a proper base of support and a uniform wear of the shoe.
The most suitable shoe is a _flat shoe_, whose outer branch must be
wider than the inner. It is so applied that the inner branch follows
the edge of the wall closely, while the outer branch must be full
and at the quarter must extend beyond the wall far enough to touch a
perpendicular line dropped from the coronet (Fig. 215). The shoe must,
therefore, be punched deep (coarse) on the outer branch and fine on
the inner. A side-clip must be placed on the outer branch, because in
time the outer half of the hoof will again be too high. _Bar-shoes and
rubber pads are injurious when both cartilages are ossified_, but may
be used when there is partial ossification of _but one cartilage_,
especially if corns are present.
[Illustration: FIG. 214. Right fore-hoof whose form has changed as a
result of ossification of the external lateral cartilage.]
[Illustration: FIG. 215. Shoe with broad outer branch, for the hoof
shown in the preceding cut.]
B. Disturbances of Continuity of the Hoof.
1. CRACKS.
Interruptions of continuity of the wall extending in the direction of
the horn-tubes are known as cracks or seams. They have, according to
their location, degree, and extent, not only various names, but also a
varying significance.
_Occurrence._—On the inner side of front hoofs, especially of horses
that stand base-wide; on hind hoofs, usually at the toe.
[Illustration: _Fig. 216._
Hoof exhibiting a coronary crack, a plantar or low crack, and a
complete deep crack, the latter with a nail ready to be clinched.]
_Classification._—According to location we distinguish toe-cracks,
side-cracks, quarter-cracks, and bar-cracks. Those cracks which affect
only the upper border of the hoof are called _coronary cracks_; those
which are limited to the lower border of the hoof are sometimes
designated _low cracks_ (plantar cracks); while those which are
continuous from one border to the other are called _complete cracks_.
If the crack passes through the entire thickness of the wall to the
sensitive tissues underneath, it is called a _deep_ or _penetrating
crack_, in contradistinction to the _superficial crack_ (Fig. 216).
_Causes._—There are many. Besides wounds of the coronet, everything
that impairs the elasticity of the horn, weakens the hoof, and causes
an overloading of one-half of the hoof. Furthermore, great dryness and
excessive work on hard streets.
_Prognosis._—This will depend upon the age, kind, and location of the
crack. A _low crack is without significance_ unless it is the remnant
of an old coronary crack which has grown down. _Coronary cracks_, on
the contrary, _are more serious_ because of the lameness which often
accompanies them, and especially on account of the long duration of the
healing process.
The borders of the crack =never= grow together, and healing can only
take place through healthy, unbroken horn growing down from the
coronary band.
(_a_) _Treatment of Coronary and Bar-Cracks._—If practicable, allow the
affected horse to go barefoot; otherwise, the use of the =bar-shoe=
for _all cracks_ is advised, because it will continuously protect the
diseased section of wall from pressure by the shoe. If there are
present still other diseases of the hoof (corns, contraction, flat or
full hoof), the addition of a leather sole with packing will be most
beneficial, not only in favoring the healing of the crack, but also in
improving the form of the hoof and in favoring the cure of the other
lesions. In all coronary cracks it is of advantage to assist healing
by fastening or immobilizing the borders of the crack by one of the
following methods:
1. By rivets (nails), which pass across the crack through holes
previously drilled in the horn (Fig. 217).
2. By clamps or hooks, which by means of special pincers are forced
into pockets previously burnt into the horn on opposite sides of the
crack (Fig. 219, B).
3. By a thin iron plate placed across the crack and secured by small
screws, such as are used in wood (Figs. 220, 221).
4. By means of a bandage to last one shoeing.
=Toe-crack= occurs most often in draught horses and most frequently
in the hind feet. In shod hoofs it starts at the coronary border, and
unless proper treatment is instituted soon reaches the plantar border.
Long toes and low quarters and excessive dryness of the horn are
predisposing causes. The exciting cause is usually forward pressure
of the upper end of the short pastern against the thin upper edge of
the wall of the toe. In the last part of the phase of contact of hoof
with ground the pasterns are upright, or may even incline downward
and backward (foot-axis broken strongly backward), the short pastern
presses the coronary band firmly against the upper thin edge of the
toe, when if brittle through dryness it is unable to stretch and tears
asunder. Thus, under the effort of starting a heavy load, when a horse
with all four legs flexed has risen upon the points of his toes, a
short quick slip followed by a catch, will frequently start a crack at
the coronet.
The hoof should be so dressed and shod that the foot-axis shall be
straight when seen from the side. In hind feet it is admissible to
break the foot-axis slightly forward. Therefore, shorten the toe and
spare the quarters. If the latter are deficient in length, raise them
by swelling the branches or by low heel-calks.
[Illustration: FIG. 217.
Toe-crack immobilized by lateral toe-clips: _a_, bearing-surface left
free from pressure; _b_, heads of the rivets (nails) driven through
holes previously drilled.]
The shoe may be open, or a bar-shoe, or a short shoe with a rubber
frog- and buttress-pad. Whatever expands the quarters closes a
toe-crack. The Defay’s shoe (Fig. 206), or the Chadwick spring beneath
a rubber pad, or beneath a bar-shoe with leather sole, if the frog
be much shrunken, will be of service. The shoe should fit air-tight,
except for an inch or so on both sides of the crack. Two lateral
toe-clips (Fig. 217) are drawn up, and the wall between these clips is
cut down from a twelfth to an eighth of an inch.
[Illustration: FIG. 218.
Spiral drill for boring the hole into which a round wire nail is driven
to fasten a toe-crack: (_a_) three sided point of drill (similar to the
point of a stilet of a cæcal trocar).]
After the shoe has been nailed on tight the toe-crack should be
immobilized. The best method is by buried nails. Slots are burned or
cut on opposite sides at a distance of an inch from the crack. With a
spiral drill (see Fig. 218) bore a hole from a slot at right angles to
the crack. Make a similar hole on the opposite side. Make the holes
continuous by introducing a straight hot wire. The rivet may be an
ordinary round wire nail which has been softened by bringing it to a
yellow heat and allowing it to cool slowly. It is driven through and
the ends firmly clinched. Such a nail is easily placed, need not press
upon fleshy leaves, can not be stripped off or lost, and holds fast.
The horse should stand on the foot while the rivet is being clinched.
Two are sufficient for a complete crack (Fig. 217).
[Illustration: FIG. 219.
_A_, Vachette burning iron for making the two slots to receive the
ends of the hook; _b_, shoulder; _B_, Vachette hook; _C_, pincers for
forcing the hook into the wall.]
A more rapid, though less efficient method of immobilizing a toe-or a
quarter-crack is by the use of the Vachette hook. A special apparatus
is required (see Fig. 219). The burning iron (Fig. 219, _A_) is brought
to a yellow heat, its end applied to the wall so that the two ears are
on opposite sides and equidistant from the crack, when it is pressed
firmly till the shoulder (Fig. 219, _b_) touches the surface of the
wall. A Vachette hook, the distance between the points of which equals
the distance between the ears of the firing iron, is seized by the
special pincers (_C_), pressed into the slots burned to receive it, and
is then driven into the horn by compressing the pincers. At the toe
these hooks are frequently stripped off by the heels of the opposite
shoe (in hind feet). Free application of hoof ointment, and maceration
of the horn by melting snow or mud tends to loosen them so that they
often drop out.
An efficient method of fastening either a toe-or a quarter-crack
is by using a metal plate one-sixteenth (¹/₁₆″) of an inch thick,
provided with four to eight holes for the reception of screws four- to
five-sixteenths of an inch long. The plate is heated, bent to conform
to the curvature of the wall and pressed against the horn till it
burns a bed for itself, when it is screwed fast. It will not loosen
(see Fig. 220, _b_). In every complete crack of the wall the growing
down of coherent horn is favored by thinning the horn for an inch on
both sides of the crack directly over the coronary band (see Fig. 221,
_a_), so that any gliding movement between the sides of the crack below
can not be transmitted through the thinned area to the crack in the
velvety tissue of the coronary band. Cutting a “V” at the coronet acts
similarly, but is less efficient.
[Illustration: Fig. 220.
Hoof with coronary quarter-crack, shod with a bar-shoe. The part of the
quarter relieved of pressure _a_, is indicated by the dotted lines;
_b_, iron plate secured by small wood screws ⁴/₁₆-⁵/₁₆ of an inch in
length.]
[Illustration: FIG. 221.
Hoof with complete quarter-crack, shod with a bar-shoe: _a_, area
thinned almost to the pododerm; _b_, ¹/₁₆ inch metal plate secured by
screw ⁵/₁₆ of an inch long; _c_, quarter relieved of pressure from
bottom of crack to a perpendicular dropped from top of crack.]
=Quarter-crack= is usually associated with contraction of the heels. It
occurs on the inner quarter of base-wide (toe-wide) hoofs, and rarely
in the outer quarter of base-narrow hoofs. For quarter-cracks we use a
bar-shoe and determine the extent of the wall to be laid free in the
following manner: We imagine the crack to be prolonged in the direction
of the horn-tubes to the plantar border, and drop a perpendicular line
from the upper end of the crack to the plantar border. That part of the
plantar border lying between these two points is then to be lowered
sufficiently to prevent pressure from the shoe until the next shoeing
(Figs. 220, _a_, and 221, _c_).
This method should be followed even when the perpendicular line falls
behind the buttress.
The crack may be immobilized by the metal plate, or by narrow ticking
bandage or adhesive tape wound a half dozen times around the hoof, in
conjunction with a bar-shoe, Chadwick spring, leather sole and tar and
oakum sole-packing.
In dressing the hoof, the side containing the crack should be spared,
the opposite side lowered, the object being to shift the weight and
consequent expansion into the sound quarter. When the affected quarter
is deficient in length the branch of the shoe beneath should be made
thicker, even to the extent of causing it to ground in advance of the
opposite branch.
Next to shoeing, rubber hoof-pads render good service, because through
them a part of the body-weight is distributed over the sole and frog.
They assist in widening the hoof, and lessen shock when the foot is set
to the ground. These are all matters which favor the growing down of
unbroken horn.
When the crack gaps widely, and the frog is small and deep in the foot
_a shoe with bar-clips_ (Defay’s shoe), or a Chadwick spring, with
bar-shoe and leather sole may be used. It is not impossible, indeed,
to obtain a cure by using an ordinary open flat shoe, though much will
depend upon the other lesions that may be present, the nature of the
hoof, and the service required of the animal.
If the edges of the crack are irregular and overlapping, they should be
carefully thinned away. Thinning the horn on both sides of the crack
over the coronary band, preventing drying out of the horn, and frequent
applications of carbolized oil to the coronet favor growth of undivided
horn and guard against a renewal of the crack.
If in the beginning of the disease there is inflammation and lameness,
cooling poultices should be used for several days. When there is no
lameness, the horse may be used for slow draft purposes. _Coach-and
saddle-horses should be kept from fast work until sound horn has grown
down at least one-half of an inch from the coronet._
_Bar-cracks_ are usually the result of changes of position of the
quarters, and are just as frequently brought about by contraction as
by leaving the quarters too high. We see them almost entirely upon the
fore-hoofs. They seldom occur alone, but are usually accompanied by
corns. When the crack extends to the pododerm there is a superficial
inflammation of the pododerm and lameness. When treatment is not
promptly begun the inflammation extends to the deeper layers of the
pododerm, or, indeed, even to the plantar cushion, and gives rise to
swelling of the bulb of the heel upon that side and to a well-marked
lameness, which requires treatment by a competent veterinarian.
Ordinarily a bar-crack is only found by a close examination of the
hoof after the shoe has been removed. In paring the hoof the crack
usually appears as a dark streak, sometimes as a bloody fissure; not
infrequently grayish hoof-pus is discovered in the depths of the crack.
The treatment must be directed towards favoring the growth of a
continuous (unbroken) bar. This is accomplished by completely removing
the edges of the crack, paring the horn of the vicinity very thin, and
preventing the least pressure upon the wall of this quarter by the
shoe, by lowering this quarter with the rasp and applying a =bar-shoe=
with leather sole.
Following the removal of the edges of the crack there often appears,
especially in stumpy hoofs, a deep groove; if the bottom of this groove
is moist, we should pack it with oakum wet with a five per cent.
solution of creolin or carbolic acid, and cover the oakum with wax
(grafting-wax). The cracks will return if the exciting causes cannot be
completely removed.
(_b_) _Treatment of Low Cracks (Plantar Cracks)._—These cracks,
occurring principally upon the hoofs of unshod horses, are the result
of excessive stretching and bending of the lower border of the wall.
Insufficient rounding of the wall with the rasp is largely responsible
for them. An exciting cause in shod horses is the use of too large
nails in shoes that are punched too fine.
Every coronary crack becomes in time a low or plantar crack, and this
has an important bearing upon the prognosis, because a renewal of the
coronary crack will be followed by a low crack.
In order to remove these cracks it is sufficient merely to shoe the
horse. Upon shod horses they may be prevented by using properly punched
shoes and thin nails. The lower border of the wall near the crack
should be relieved of pressure by cutting out a half-moon-shaped piece
of horn. To prevent the crack from extending farther upward we may burn
a transverse slot at the upper end of the crack, in as far as the leafy
layer of the wall, or cut such a slot with a small hoof-knife.
2. CLEFTS.
An interruption of continuity of the wall, at right angles to the
direction of the horn-tubes, is called a _cleft_.
Clefts may occur at any part of the wall; yet they occur most often
upon the inner toe and inner side, as a result of injury from sharp,
improperly placed heel-calks (see page 173). However, suppurating
corns, or other suppurative processes situated at the coronet or which
find their point of escape at the coronet, may from time to time lead
to separations of continuity and the formation of horn-clefts.
[Illustration: FIG. 222. Hoof with clefts of the toe and side wall.]
Horn-clefts, though the result of lesions which are often very
injurious and interfere with the use of the horse, are of themselves
not an evil which can be abolished or healed by shoeing, although, in
many cases, proper shoeing would have prevented them. A horn-cleft is
not a matter for consideration by the shoer until it has grown down so
far that it comes within the region of the nails.
In order not to disfigure the hoof unnecessarily, the horn below the
cleft should be kept in place as long as possible by shortening the
wall at that point, to remove shoe-pressure, and by driving no nails
into it. If, however, the horn is loose and about to come away, it
should be removed and the defect filled with Defay’s patent horn-cement.
3. LOOSE WALL.
Separation of the wall from the sole _in the white line_ is called
loose wall (Fig. 223, _a_).
_Occurrence._—Frequent on the fore-hoofs of shod and unshod horses,
and oftener upon the inner than upon the outer side. More rare on hind
hoofs. Common-bred horses with wide and flat feet are predisposed to
this trouble.
We distinguish _superficial_ and _deep loose wall_; only the latter
requires the shoer’s attention, because it leads to lameness.
_Causes._—Walls which are very oblique (slanting); outward bendings of
the plantar border of the wall; burning the horn with hot shoes;
dryness; neglected shoeing; excessive softening of the horn with
poultices, particularly of cow-dung; carelessness in preparing the
bearing-surfaces of hoof and shoe in shoeing; uneven fitting of the
shoe.
_Treatment._—It aims to remove the lameness and to favor growth of
coherent horn. In the first place the removal of the exciting causes,
followed by proper shortening of the wall. We should apply a shoe whose
bearing-surface _inclines slightly downward and inward_, is perfectly
smooth, and wide enough to cover the wall, white line, and outer border
of the sole; the iron should be only moderately warm. Where there is
lameness we use a leather sole with packing, or a =bar-shoe=. The loose
wall should be freed from shoe-pressure only when it does not extend
far along the white line. When the separation is extensive the loose
wall should not be lowered. The crack should be filled with wood-tar,
crude turpentine, or soft grafting-wax.
If a loose wall occur upon the foot of a horse while running barefoot,
all separated horn should be removed; if, on account of the nature of
the ground, this seems to be impracticable, the hoof must be shod.
_Care of the Hoof._—Shoe at least every four to five weeks. Preserve
the pliancy and toughness of the horn by judicious moistening.
4. HOLLOW WALL.
A _hollow wall is one in which a separation has occurred between the
middle layer of the wall and the keraphyllous layer_. This crack or
separation always extends in the direction of the layers of the wall
(Fig. 223, _b_).
[Illustration: FIG. 223. An imaginary transverse vertical section of a
hoof showing (_a_) loose wall and (_b_) hollow wall.]
_Occurrence._—Quite rare.
We should suspect a hollow wall when a part of the wall _rounds out
prominently beyond the rest_, and gives forth a hollow (resonant) sound
when struck. The white line presents a crack, yet we should hesitate to
form a conclusion as to the extent of the separation from the extent of
the crack along the white line, since the latter may be considerably
smaller. The separation extends higher up the wall than in the case of
loose wall, frequently to the coronet. The cavity is usually filled
with crumbling, disintegrated horn.
Hollow wall is not often accompanied by pain. Lameness may arise,
however, if the hollow section of wall assists in bearing the
body-weight, and if the animal does fast work upon paved streets.
_Causes._—Mechanical influences resulting in chronic inflammation of
fleshy leaves.
_Treatment._—A cure is possible, but requires considerable time. In
shoeing, which should always aim to _relieve pressure_ from the hollow
section of wall, we cleanse the cavity and fill it with oakum and tar,
crude turpentine, or wax. Where the separation is very extensive we use
a _bar-shoe_.
The time required for complete cure of hollow and loose walls will
depend upon the height of the separation (see growth of the hoof, page
82).
5. THRUSH OF THE FROG.
When the horny frog is ragged and fissured, and an ill-smelling,
dark-colored liquid collects in the lacunæ of the frog, it is affected
with thrush. When thrush exists uninterruptedly for several months the
perioplic band is irritated and forms rings of periople which assume an
irregular course and cross the rings of the middle layer of the wall
(Fig. 224).
[Illustration: FIG. 224. Hoof with irregular superficial rings
resulting from thrush of the frog.]
The _causes_: uncleanliness, =too little exercise= in fresh air,
excessive paring of the frog, and the use of shoes with calks by which
the frog is permanently removed from the ground.
The _consequences_ are, besides contraction of the hoof, soreness in
travelling, a shortening of the step, and, occasionally, well-marked
lameness.
_Treatment._—Removal of all greasy horn from the frog, and of the
prominent overgrown angles of the buttresses (see page 100), thorough
washing of the frog once or twice daily with a 5 per cent. creolin or
carbolic solution, =abundant exercise=, and shoes without calks.