Diseases of the Horse's Foot Part 7

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

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their point of emergence on the wall, and the condition of their broken ends all being carefully noted as they are withdrawn.

The removed shoe should next be examined as to the coa.r.s.eness or fineness of its punching and the 'pitch' of its nail-holes, and close attention given to the shape of its bearing surface.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

To the cocaine other pract.i.tioners add morphia in the following proportions:

Cocaine hydrochlorate 2-1/2 grains.

Morphia 1-1/2 "

Aqua destil 1-1/2 drams.

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

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

[Footnote A: The _Journal of Comparative Pathology and Therapeutics_ vol.

viii., pp. 27, 43.]

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

_Five Minutes_.--Lameness perceptibly diminished.

_Ten Minutes_.--Lameness scarcely perceptible.

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

_Ten Minutes_.--No lameness, thus proving that the seat of lameness was below the point of injection.

CASE III.--Cab gelding, aged, free clinique; Messrs. Elme's and Moffat's case. Obscure lameness; foot suspected of navicular disease; very lame.

Injected 30 minims of a 5 per cent. solution of cocaine on either side of the leg over the metacarpal nerves.

_Six Minutes_.--Lameness perceptibly less; there was no response whatever on the inside of the leg to the p.r.i.c.k of a pin. On the outside, which had not been injected so thoroughly, there was sensation, although not so much as in a healthy foot.

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

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

[Footnote A: _Loc. cit_.]

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

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

CHAPTER V

GENERAL REMARKS ON OPERATIONS ON THE FOOT

A. METHODS OF RESTRAINT.

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

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

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

[Ill.u.s.tration: Fig. 38--The BLIND.]

[Ill.u.s.tration: Fig. 39--THE SIDE-LINE.]

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

[Ill.u.s.tration: FIG. 40.--THE SIDE-LINE ADJUSTED PREPARATORY TO SECURING THE NEAR HIND-FOOT.]