Shelly Hoofs (or splitting open of the external part of the horny hoof).—The feet of some horses are more subject to this disease than those of others, from the fibrous structure being more dry with them.
This fibrous structure forming the hoof is found, on microscopic examination, to resemble a lot of hairs all glued together into a hardened mass, and where the adhesive matter is of a drier character than usual, the hoofs are more brittle. With some horses this results in “shelly hoofs;” they don’t split, but are perpetually breaking away. With this description of hoofs, tar is the best possible application. Neither grease nor oil should ever be used—these only aggravate the disease, as on close observation they will be found to act as powerful astringents, excluding the healthy action of air and moisture upon the part most in need of them. Strange to say, tar, from its pungent properties, induces healthy action in the part, and is peculiarly adapted to promote the growth of the fibrous structure as well as lubricating it.
Sand-Cracks seldom go diagonally, but are either horizontal or vertical. I shall endeavour to exemplify the simple principle of this disease with a simple principle of remedy, dealing with it like a split in a board on which I desired to put an effectual stopper. In such a case I should carefully gouge out a small hole at each end of the split, beyond which hole the fissure would be certain not to pass. With the hoof the same principle can be carried out by filing an indentation directly across each end of the crack, only taking care not to file deeper than the insensible part of the hoof; or the end will be answered by using a red-hot firing-iron instead of a file, taking the same precaution not to touch the sensible part. I should also weaken along the edges of the crack itself by rasping them down. Over the crack, if deep, should be strapped a thin pad of tow and tar, to induce reproduction and prevent foreign substances from entering the fissure.
Unless by the grossest neglect, no sand-crack will have been allowed to go beyond the reach of the foregoing treatment, but in some cases the effect of negligence and ignorance is seen in the horizontal crack running almost round the foot. In such cases it will generally be found that with a flat foot (inclined to greater malformation) the toes have been suffered to extend, shoeing after shoeing, by the smith allowing a great accumulation of wall over the toe, until the centre has become weakened into a fissure. Such a state of things seldom or never occurs in a gentleman’s stable, but is to be met with among farm-horses or those accustomed to heavy draught.
The careful strapping-up with tar and tow, which must be constantly attended to, rest, and the indentation process, will, with time and care, effect a cure.
Sand-crack, especially the vertical, is more dangerous and tedious the nearer it is to the coronet. This once divided, the case becomes serious, the coronet being very vascular, and a split here requires a great deal of care to induce it to take on union. Unless the closing commences at the coronet, and continues as the hoof grows down, it will never close at all; in fact, if the coronet be divided, it is fortunate if the crack does not go the whole way down to the shoe. If it does not, the lower end should be weakened by filing an indentation at its lower extremity, weakening the sides of the crack by rasping them, and keeping the hoof strapped round with dressings of tar and tow, also (a most important part of the treatment) paring away the wall of the foot (above the shoe and immediately under the crack) an inch—that is, half an inch on each side of it—making as large a vacuum as can with safety to the sensible parts of the foot be pared away, directly under the crack and over the shoe; the object of this being that all parts of the wall except that under the crack shall press on the shoe. It is obvious that by the above means every movement of the horse, in place of aggravation, will tend towards alleviation of the disease, by pressing the weakened sides of the fissure together. For the foregoing reasons, in the case of a vertical crack the shoes had better remain on, while in the worst cases of the horizontal crack, as its weight round the bottom tends to weaken the centre of the hoof where the crack is likely to be situated, it had better be removed (or light tips worn), its absence also enabling the wall of the hoof under the crack to be rasped as thin as possible. In vertical cracks the use of a bar-shoe will tend to keep the foot together ([page 81]).
Corns are occasioned by the inflexible shoe pressing on that part of the sole, or possibly from friction of the bones upon its internal surface. They present the appearance of a red effused bruise, almost invariably situated on the heel of the sole of the inside quarter of the fore feet.—[See illustration, fig. 3, page 130.]
When neglected, they occasion severe lameness, and go on to suppuration.
Broken knees are also frequently the result of neglected corns.