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 Circ.u.mference 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.

[Ill.u.s.tration: 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 quant.i.ty 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 pract.i.tioners, with the wedge, apply also a clamp, thus a.s.suring 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.

[Ill.u.s.tration: FIG. 91.---THE BEARING 'EASED' BY REMOVAL OF THE WALL.]

[Ill.u.s.tration: 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 ill.u.s.trates 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 partic.i.p.ate unduly in the downward movement, and so tend to widening of the crack at its highest point.

[Ill.u.s.tration: 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 subst.i.tuted.

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 a.s.sist 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 haemorrhage, 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).

[Ill.u.s.tration: FIG. 94, FIG. 95, FIG. 96. In Figs. 94, 95, and 96 the thick black lines ill.u.s.trate 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 partic.i.p.ating 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 advent.i.tious 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 haemorrhage 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.

[Ill.u.s.tration: FIG. 97. The dotted lines outline the V-shaped portion of wall to be removed in the treatment of complicated toe-crack.]

[Ill.u.s.tration: 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 haemorrhage and the accompanying inflammatory phenomena occasioned by the injury.

Thus, with the haemorrhage we get ecchymosis, and consequent red staining of the surrounding structures. As is the case with extravasations of blood elsewhere, the haemoglobin 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.

_Cla.s.sification_.--Putting on one side the cla.s.sification 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 cla.s.sify corns according to the changes just described.