The activity of the cells of the rete Malpighii of the corium covering the remainder of the foot will be quite as necessary as the activity of the cells of the coronary papillae which form the horn tubes themselves. 'For,' in Professor Mettam's own words, 'I am inclined to believe that much of the "white line" which is found uniting the wall of the hoof to the sole has been derived from the horn formed from the rete of the foot corium. This origin will explain the absence of pigment from this thin uniting "line," as it does from the horn lining the interior of the wall. The cells of the rete are free of colouring matter.'



From the matter here given us it is easy to understand how, in a macerated foot, the appearance is given of interlocking of the sensitive and horny laminae. We see that the horny laminae are ingrowths of the rete Malpighii, ploughing into and excavating the corium into the shape of leaves—the sensitive laminae. Putrefactive changes simply break into two separate portions what originally was one whole, by destroying the cells along its weakest part. This part is the line of soft protoplasmic cells of the rete Malpighii. Thus the more resistant parts (the horn on the one hand, and the corium covering the foot on the other) are easily torn asunder.

As a result of the evidence we have quoted, we are able to answer our original question in the affirmative. Seeing that the horny and the sensitive laminae are both portions of the same thing—namely, a modified skin, in which the epidermis is represented by the horny laminae, and the corium by the sensitive—it is clear to see that the cells covering the inspreading horny laminae are dependent for their growth and reproduction upon the cells with which they are in immediate contact—namely, those of the sensitive laminae—and that therefore the sensitive laminae are responsible for the growth of the horny.

B. CHEMICAL PROPERTIES AND HISTOLOGY OF HORN.

Horn is a solid, tenacious, fibrous material, and its density in the hoof varies in different situations. It is softened by alkalies, such as caustic potash or soda and ammonia, the parts first attacked being the commissures, then the frog, and afterwards the sole and wall. Strong acids, such as sulphuric acid and nitric acid, also dissolve it.

The chemical composition of the hoof shows it to be a modification of albumin, its analysis yielding water, a large percentage of animal matter, and materials soluble and insoluble in water. The proportions of these, as existing in the various parts of the hoof, have been given by Professor Clement as follows:

Wall. Sole. Frog. Water 16.12 36.0 42.0 Fatty matter 0.95 0.25 0.50 Matters soluble in water 1.04 1.50 1.50 Insoluble salts 0.26 0.25 0.22 Animal matter 81.63 62.0 55.78

Horn appears to be identical with epidermis, hair, wool, feathers, and whalebone, in yielding 'keratin,' a substance intermediate between albumin and gelatine, and containing from 60 to 80 per cent. of sulphur.

That horn is combustible everyone who has watched the fitting of a hot shoe knows. That it is a bad conductor of heat, the absence of bad after-effects on the foot testifies.



In a previous page we have described the manner of growth of the horn tubules, and noted the direction they took in the wall; also, we have noticed the existence between them of an intertubular horn or cement.

Those who wish to give this subject further study will find an excellent series of articles by Fleming in the Veterinarian for 1871. We shall content ourselves here with introducing one or two diagrams and photo-micrographs, and dealing with the histology very briefly.

Under the microscope the longitudinal striation of the wall is found to be due to the direction taken by the horn tubules.

Fig. 31 is a magnified perpendicular section of the wall. In it the parallel dark striae are the horn tubules in longitudinal section. The lighter striae represent the intertubular material.

Fig. 32 gives us the wall in horizontal section. To the left of this picture we find the horn tubules cut across, and standing out as so many concentrically ringed circles. In the centre of the figure are seen the horny laminae, with their laminellae, and the sensitive laminae. The right portion of the figure pictures the corium.



Fig. 33 is, again, a horizontal section, cut this time at the junction of the wall with the sole. To the left are seen, again, the horn tubules of the wall, and to the centre the horny laminae. In this position, however, the structures interdigitating with the horny laminae are not sensitive, but are themselves horny. As the diagram shows, they contain regularly arranged horn tubules cut across obliquely. It is this horn which forms the 'white line.' To the extreme right of the figure are seen the horn tubules of the sole.

There remains now but to notice the arrangement of the horn tubules in the frog. The peculiar, indiarubber-like toughness of this organ is well known. Histological examination gives a reason for this.



The horn tubules of the frog are sinuous in their course. This is accounted for by the fact that in the horn of the frog there is a large amount of intertubular material, this having the effect of frequently turning the horn tubules from the straight. In addition to this, the intertubular material has a peculiar arrangement of the cells composing it. These are laid down in alternating striae (1) of cells with their long axes longitudinal, and (2) of cells with their long axes horizontal. This is seen in Fig. 34, between the long papillae of the corium, where the lines of longitudinally arranged cells in horizontal section stand out darker than the adjoining strata in which their arrangement is horizontal. The tortuous direction of the horn tubules, and the almost interlocking nature of the alternating strata of the intertubular material, together combine to give the frog its characteristic toughness and resiliency.

C. EXPANSION AND CONTRACTION OF THE HOOF.

Among other questions productive of heated argument come those relating to expansion of the horse's hoof. In the past many observers have strenuously insisted on the fact that expansion and contraction regularly occur during progression. Opposed to them have been others equally firm in the belief that neither took place. Quite within recent times this question also has been settled once and for all by the experiments of A. Lungwitz, of Dresden. His conclusions were published in an article entitled 'Changes in Form of the Hoof under the Action of the Body-weight.'[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. iv., p. 191. The whole of the matter in this article, from which we have borrowed Figs. 35 and 36, is too long for reproduction here. It forms, however, most instructive reading, and its careful perusal will well repay everyone interested in this most important question (H.C.R.).]

In connection with this it is interesting to note how, all unconsciously, two separate observers were simultaneously arriving by almost identical means at an equally satisfactory answer to the question. Prior to the publication of Lungwitz's article on the subject, Colonel F. Smith, A.V.D., had arrived at similar conclusions by working on the same methods.



It is unnecessary for our purpose here to minutely describe the exact modus operandi of these two experimenters. Briefly, the method of inquiry adopted in each case was the 'push and contact principle' of the ordinary electric bell, and the close attention which was paid to detail will be sufficiently gathered from Figs. 35 and 36.

[Illustration: Fig. 36. I. LEFT FORE-FOOT SHOD AND MOUNTED TO RECOGNISE THE SINKING OF THE SOLE. a, Iron plate covering the inner half of the horny sole; b, openings in the same, with screw-holes for the reception of the contact-screw c (the part of the sole under the plate is covered with tinfoil, which at d passes out under the outer branch of the shoe, and becomes connected with the tinfoil of the wall; in order to give the freshly applied tinfoil a better hold, copying-tacks are at e passed through it into the horn, and one is similarly used to protect the tinfoil at the place where the contact-screw touches the latter); f, holes with screw thread for the fastening of the angle required to measure the movement of the wall, and also for the fastening of the conducting-wire, g; h, conducting-wire passing from the tinfoil; i, isolated nails.]



After numerous experiments with the depicted contact-screws, moved to the various positions indicated in the drawings, the following conclusions were arrived at:

1. BEHAVIOUR OF THE CORONARY EDGE.—During uniform weighting of all four hoofs the coronary edge shows a tendency to contraction in the anterior and lateral regions of the hoof, and a tendency to expansion posteriorly. With heavy weighting of the hoof, which is shown by a backward inclination of the fetlock, contraction in the anterior and lateral regions is slight, but the expansion behind, in the region of the heels, is distinct, commencing gradually in front, becoming stronger, and diminishing again posteriorly. The coronary edge of the heels becomes slightly bulged outwards. The bulbs of the heels swell up and incline a little backwards and downwards.

When the fetlock is raised the expansion of the coronary edge of the heels disappears from behind forwards, passing forwards like a fluid wave. In the lateral and anterior regions of the coronary edge the contraction disappears; and when the weight is thrown off the foot it passes into a gentle expansion of the coronary edge of the toe. During the opposite movement of the fetlock, that of sinking backwards, this change of form is executed in the converse manner.

In short, the coronary edge resembles a closed elastic ring, which yields to pressure, even the most gentle, of the body-weight, in such a way that a bulging out of any one part is manifested by an inward movement of another part.

In Fig. 37, b, the dotted line represents the changes of form in comparatively well-formed and sound hoofs at the moment of strongest over-extension[A] of the fetlock-joint.

[Footnote A: The term 'over-extension,' as employed by Lungwitz, is intended to indicate that position assumed by the fetlock-joint when the opposite foot is raised from the ground.]

2. BEHAVIOUR OF THE SOLAR EDGE.—Under the action of the body-weight this is somewhat different from that of the coronary edge. Anteriorly, and at the sides, as far as the wall forms an acute angle with the ground, the tendency to expansion exists, but the change of form first becomes measurable in the region where the lateral cartilages begin. Quite posteriorly the expansion again diminishes.

Fig. 37, a, by the dotted line represents the expansion at the moment of over-extension of the fetlock-joint. This expansion is itself rather less than at the coronary edge, and it shows itself distinctly only when the weighted hoof is exposed to a counter-pressure on the sole and frog, no matter whether the counter-pressure is produced naturally or artificially. Thus anything tending to the removal of the pressure from below, such as a decayed condition of the frog or excessive paring in the forge, will diminish the extent of expansion of the solar edge.

Contraction of the solar edge of the heels occurs at the moment of greatest over-extension of the fetlock-joint—that is, in a foot with pressure from below absent. On the face of it, this appears impossible. Lungwitz, however, has perfectly demonstrated it; and, when dealing with the functions of the lateral cartilages in a later paragraph, we shall show reason for why it is but a simple and natural result of the foot dynamics.

3. BEHAVIOUR OF THE SOLE.—The horny sole becomes flattened under the action of the body-weight. This is most distinct at the solar branches, and gradually shades off anteriorly and towards the circumference. As might be supposed, width of hoof and thickness of the solar horn exert an influence on the extent of this movement. The sinking of the horny sole is most marked in flat hoofs.

D. THE FUNCTIONS OF THE LATERAL CARTILAGES.[A]

[Footnote A: Extracted from a paper by J.A. Gilruth, M.R.C.V.S., in the Veterinary Record, vol. v., p. 358.]

We have just referred to contraction of the heels as taking the place of a normal expansion in those cases where ground frog-pressure was absent. We shall readily understand this when we bear in mind the anatomy of the parts concerned, especially that of the plantar cushion. This wedge-shaped structure we have already described as occupying the irregular space between the two lateral cartilages, the extremity of the perforans tendon, and the horny frog.

Now, when weight or pressure is exerted from above on to this organ, and the frog is in contact with the ground below, it is clear from the position the cushion occupies that, whatever change of form pressure from above will cause it to take, it must certainly be limited in various directions.



Because of the shape of the cushion its change of form cannot be forwards (simultaneous pressure from above and below on to this wedge with its apex forwards must tend to give it a backward change of form). Because of the pastern being horizontal, and aiding in the downward pressure, its change of form cannot be upwards. And because of the ground it cannot be downwards. It follows, therefore, that the movement must be backwards and outwards, being especially directed outwards because of its shape and the median lacuna in its posterior half—this latter, the lacuna, accommodating as it does the frog-stay, preventing the tendency to backward movement becoming excessive, and directing the change of form to the sides. Where the greatest pressure is transmitted, then, is to the inner aspects of the flexible lateral cartilages. The coronary cushion being continuous with the plantar, the backward and outward movements of the latter will tend to pull upon and tighten the former, especially in front. This will account for the contraction noted by Lungwitz in the anterior half of the coronary edge of the hoof.

Remove the body-weight, and naturally the elastic nature of the lateral cartilages and the coronary and plantar cushions, with, in a less degree, that of the hoof, cause things to assume their normal position.

Repeat the weighting of the hoof, in this second case without frog-pressure, and we shall see at once that we have done away with one of the greatest factors in determining the outward and backward movements of the plantar cushion—namely, the pressure from below on its wedge-shaped mass. The movement of the plantar cushion will now be downwards as well as backwards; and, seeing that it is attached to the inner aspect of each lateral cartilage, we shall expect these latter, by the downward movement of the plantar cushion, to be drawn inwards. This Lungwitz has shown to occur.

The chief function of the lateral cartilages, therefore, is to receive the concussion engendered by locomotion, which concussion is directed backwards and outwards by the pad-like plantar cushion.

In addition to this, the lateral cartilages, together with the plantar and coronary cushions, play the part of a valve to the whole of the veins of the foot.

It is in this way: We have only to refer to the chapter on anatomy to see that the whole of the foot is covered with a tissue of extreme vascularity. Thus we find papillae—the over the coronary cushion; enlarged and modified papillae sensitive laminae—covering the anterior face of the os pedis; and numberless papillae again covering the sole. There can be no doubt that the quantity of fluid brought by the bloodvessels of these papillae to the foot acts largely as a means of hydraulic protection to the soft structures.[A] In like manner as that delicate organ, the brain, is best protected by being floated upon the cerebro-spinal fluid and bloodvessels (which fluids transmit waves of concussion or pressure through the organ without injury to the delicate cells forming it), so, in like manner, does the extreme vascularity of the foot protect the cells of its softer structures from the effects of pressure and concussion.

[Footnote A: The Veterinary Record, vol. iii., p. 518.]

That this law of hydraulics may operate in the horse's foot to the best advantage, the veins must be provided with valves, and valves of no mean strength. These we know to be absent. It is here that the lateral cartilages and the elastic substances of the coronary and plantar cushions step in to supply the deficiency.

At the time when weight is placed upon the foot (with, of course, a tendency to drive the blood upwards in the limb), and, therefore, the time when a valvular apparatus is needed to retain the fluid in the foot, we find the wanting conditions supplied by the pressure outwards of the plantar cushion compressing the large plexuses of veins on each side of the lateral cartilages, to which plexuses, it will be remembered, the bulk of the venous blood from the foot was directed. A more perfect valvular apparatus, automatic and powerful, it would be difficult to imagine.

E. GROWTH OF THE HOOF.

We will conclude this chapter with a few brief remarks on the growth of the hoof. That the rate of growth is slow is a well-known fact to every veterinarian, and it will serve for all practical purposes when we state that, roughly, the growth of the wall is about 1/4 inch per month. This rate is regular all round the coronet, from which it follows that the time taken for horn to grow from the coronary edge to the inferior margin will vary according as the toe, the quarters, or the heels are under consideration.

As might naturally be expected, the rate of growth will depend on various influences. Any stimulus to the secreting structures of the coronet, such as a blister, the application of the hot iron, or any other irritant, results in an increased growth. Growth is favoured by moisture and by the animal going unshod, as witness the effects of turning out to grass. Exercise, a state of good health, stimulating diets—in fact, anything tending to an increased circulation of healthy blood—all lead to increased production of horn. With the effects of bodily disease and of ill-formed legs and feet on the wear of the hoof, and the growth of horn, we shall be concerned in a future chapter.



CHAPTER IV

METHOD OF EXAMINING THE FOOT

As a general rule, it may be taken that most diseases of the foot are comparatively easy of diagnosis. When, however, the condition is one which commences simply with an initial lameness, the greatest care will have to be exercised by the practitioner.

What remarks follow here should rightly be confined to a treatise on lameness. This much, however, we may state: As compared with lameness arising from abnormal conditions in other parts of the limb, that emanating from abnormalities of the foot is easy of detection. With a case of lameness before him, concerning which he is in doubt, the practitioner remembers that a very large percentage may safely be referred to the foot, and, if wise, subjects the foot to a rigorous examination.

Much may be gathered by first putting the animal through his paces. When at a trot, notice the peculiarity of the 'drop,' whether any alteration in going on hard or soft ground, and watch for any special characteristic in gait. At the same time inquiry should be made as to the history of the case; its duration; whether pain, as evidenced by lameness, is constant or periodic; the effect of exercise on the lameness; and the length of time elapsed since the last shoeing.

This failing to reveal adequate cause for the lameness in any higher part of the limb, one is led, by a process of negative deduction, to suspect the foot. If 'pointing' is a symptom, its manner is noticed. The foot is compared with the other for any deviation from the normal. In some cases the two fore or the two hind feet may differ in size. Though this may not necessarily indicate disease, it may, nevertheless, be taken into account if the lameness is not easily referable to any other member. Measurement with calipers will then be of help, and a pronounced increase in size, especially if marked in one position only, given due consideration. The hand is used upon each foot alternately to look for change of temperature, to detect the presence of growths small enough to escape the eye, and to discover evidence of painful spots along the coronet.

At this stage the method of percussion recommends itself, and in many cases no more useful diagnostic agent is to be found than the ordinary hammer. As a preliminary, the foot of the sound limb should be always tapped first. This precaution will serve to bring to light what is frequently met with—the aversion nervous animals sometimes exhibit to this manner of manipulation of the hoof. Unless this is done, the ordinary objection to interference is apt to be read as evidence of pain. No aversion to the method being shown, the suspected foot is gently tapped in various places round the wall, a keen look-out being kept for any manifestation of tenderness. This may vary from a slight resentment to each tap, indicated by a sudden lifting and setting down again of the foot, to a complete removal of the foot from the ground, and a characteristic pawing of the air that points out clearly enough the seat of pain.

Evidence of pain once given, the tapping is persisted in until, in some cases, the exact position of the tender spot is definitely located.

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 coarseness 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 pass 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 coarseness 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 prick of the foot.

This done, more than usual care should be taken in following up any other small prick 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 assure 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 deg. or 50 deg. 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 practitioners 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 illustrating 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 prick 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 pricks, 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.



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.



Here the side-line has formed upon it a loop sufficiently large to form a collar. This is placed round the animal's neck, the free end of the line run round the pastern of the desired foot, and the foot drawn forward, as in Fig. 40.

The loose end of the line is then twisted once or twice round the tight portion, and finally given to an assistant to hold (see Fig. 41). The foot is thus held from the ground, and violent kicking movements prevented.

Where the operation is a major one, restraint of a distinctly more forcible nature becomes imperative. Many of the more serious operations can most advantageously be performed with the patient secured in some form or other of stock or trevis, and the foot suitably fixed. It is not the good fortune of every veterinary surgeon, however, to be the lucky possessor of one of these useful aids to successful operating. Perforce, he must fall back on casting with the hobbles (Fig. 42).



With the use of these we will assume our readers to be conversant, and will imagine the animal to be already cast. It remains, then, but to detail the most suitable means for firmly fixing the foot to be operated on.

Here the side-line is again brought into use. Care should previously have been taken when casting to throw the animal so that the portion of the foot to be operated on, whether inside or outside, falls uppermost, and that the buckle of the hobble on that particular foot is placed so that it also is within easy reach when the animal is down.

In the case we are illustrating the point of operation was the outside of the near hind coronet. We will, therefore, describe the mode of fixing the near hind-foot upon the cannon of the near fore-limb.



The side-line is first adjusted as follows: It is fixed upon the cannon of the near hind-leg (A) by means of its small loop. From there it is passed under the forearm of the same limb, over the forearm, under the rope running from A to B; from there over and under the thigh, to be finally brought in front of the thigh, and below the portion of rope running from arm to thigh. The loose end of the side-line is then given to an assistant standing behind the animal's back, the buckle of the hobble restraining the foot unloosed, and strong but steady traction brought to bear from behind upon the line. The operator should now stand in front of the fore-limbs, and, by placing a hand on the rope passing round the arm, prevent the line from slipping below the knee.

By this means the hind-limb is pulled forward until the foot projects beyond the cannon of the front-limb. When that position is reached, the operator grasps the hock firmly with one hand, and, directing the side-line to be slackened, gently slides downward the coils of rope round the arm and thigh until they encircle the cannons of both limbs. The cannon of the hind-limb is firmly lashed to the cannon of the fore, and the foot firmly and securely fixed in the best position for operating (see Fig. 44).



Similarly, with the horse still on his off side, the off hind-limb may be fixed to the near fore, and the near fore and the off fore to the near hind.

With the animal on his near side, we may fix the near hind and the off hind to the off fore, and the off fore and near fore to the near hind.

The points to be remembered in fixing the limbs thus are: (1) The side-line should always commence upon the cannon of the limb to be operated on; (2) it should next pass under and over (or over and under, it is immaterial which) first the arm and then the thigh, or the thigh and the arm, as the case may be; (3) in every case, whether rounding the thigh and the arm from above or below, the piece of rope completing the round should always finish below that portion preceding it, so that traction upon it from behind the animal's back should tend to keep all portions of it from slipping below the knee and the hock.

With the uppermost fore-limb secured to the hind-limb in the manner we have described, we have the underneath fore-limb suitably exposed for both the higher and lower operations of neurectomy. The position for this operation will be made better still if the lowermost limb (the one to be operated on) is removed from the hobbles and drawn forward by an assistant by means of a piece of rope fastened to the pastern.

Taking what we have described as a general guide, other modifications of thus securing the foot will suggest themselves to the operator to meet the special requirements of the case with which he is dealing.

Regarding the administration of chloroform, no description of the method is needed here, as it will be found fully detailed in most good works on general surgery. Where great immobility is needed, it is one of the most valuable means of restraint we have. Apart from that, its use in any serious operation is always to be advocated, if only on the score of humane consideration for the dumb animal helpless under our hands.

B. INSTRUMENTS REQUIRED.

In addition to those required for operations on the softer structures—such as scalpels, forceps, artery forceps, directors, scissors, etc.—the surgery of the foot demands instruments specially adapted for dealing with the horn.

A great deal will depend upon the operator as to whether these are few or many. The average man of resource will deem a smith's rasp and one or two strong drawing-knives amply sufficient, and on no account should they be omitted from the list of those ready to hand.



The ordinary smith's drawing-knife (Fig. 45) is well known to almost everyone, and is well suited for much of the rougher part of the work. The careful following up of pricks, however, and some of the more special operations demanding removal of portions of the lateral cartilages call for instruments of a more delicate character and peculiar construction. These are to be found in the so-called sage-knife, and the modern (French) pattern of drawing-knife.



The modern drawing-knife differs from the smith's instrument in being attached to a straight, instead of a curved, handle, and in usually being sharp on both edges instead of only on one. These are made in various sizes (Fig. 46, a, b), and the blades flat, curved on the flat, or curved at an angle with the edges of the haft.

The sage-knife, as its name indicates, is a knife with a lanceolate-shaped blade. These also may be obtained in varying forms and sizes (Fig. 46, c, d, e). Fig. 46, c, is a single-edged, right-handed sage-knife. Fig. 46, d, is a left-handed instrument of the same type. The double-edged sage-knife is represented in Fig. 46, e.



It may be mentioned too, in passing, that the ordinary Symes's abscess-knife (Fig. 47) is a most useful instrument when performing the operation of partial excision of the lateral cartilages, its peculiar shape lending itself admirably to the niceties of the operation.

One or two good-shaped firing-irons will also be found useful. They will lighten the labour of tediously excavating grooves with the knife, where that procedure is necessary; and, used in certain positions to be afterwards described, will afford just that necessary degree of stimulus to the horn-secreting structures of the foot, which the use of the knife alone will not.

The man in country practice will also be well advised in carrying to every foot case a compact outfit, such as that carried by the smith. This will consist of hammer and pincers, drawing-knife and buffer. Much valuable time is then often saved which would otherwise be wasted in driving round for the nearest smith.

There are other special operations requiring the use of specially-devised instruments for their successful carrying out. These we shall mention when we come to a consideration of the operations in which they are necessary.

C. THE APPLICATION OF DRESSINGS.

One of the most common methods of applying a dressing to the foot is poulticing. Usually resorted to on account of its warmth-retaining properties, the poultice may also be medicated. In fact, a poultice, strongly impregnated with perchloride of mercury or other powerful antiseptic, is a useful dressing in a case of a punctured foot, or a wise preliminary to an operation involving the wounding of the deeper structures. The poultice may consist of any material that serves to retain heat for the longest time. Meal of any kind that contains a fair percentage of oil is suitable. Crushed linseed, linseed and bran, or linseed-cake dust are among the best.

To prepare it, all that is necessary is to partly fill a bucket with the material and pour upon it boiling water. The hot mass is emptied into a suitable bag, at the bottom of which it is wise to first place a thin layer of straw, in order to prevent the bag wearing through, and then secured round the foot. This is generally done by means of a piece of stout cord, or by straps and buckles fastened round the pastern and above the fetlock.

An improved method of fastening has been devised by Lieutenant-Colonel Nunn:

'A thin rope or stout piece of cord about 5 feet long is doubled in two, and a knot tied at the double end so as to form a loop about 5 or 6 inches long, this length depending on the size of the foot (as at A, Fig. 48). The poultice or other dressing is applied to the foot, and the cloth wrapped round in the ordinary way, the loop of the cord being placed at the back of the pastern (as in A, Fig. 49); the ends of the cord are passed round, one on the inside and the other on the outside, towards the front (as in B, Fig. 49). These ends are then twined together down as far as the toe (see C in Fig. 49). The foot is now lifted up, and the ends of the cord (CC, Fig. 49), are passed through the loop A (as at D, Fig. 49), and then drawn tight. The ends of the cord are now separated, and carried up to the coronet (as at EE, Fig. 49), one on the outside, the other on the inside of the foot. They are then again twisted round each other once or twice (as at F, Fig. 50), and are passed round the pastern once or twice on each side. They are now passed under the cord (E, Fig. 49), and then reversed, so as to tighten up E, and are finally tied round the pastern in the usual manner. The arrangement of the cords on the sole is shown in Fig. 51, which is a view from the posterior part.



'The advantages of this method of fastening have been found to be: (1) It does not chafe the skin; (2) if properly applied it has never been known to come undone; (3) it is the only way we know that a poultice can be satisfactorily applied to a mule's hind-foot; (4) horses can be exercised when the poultice is on the foot, which is almost impossible with the ordinary leather boot; (5) the sacking or canvas does not cut through so quickly.'



A further method of applying the poultice is by using one of the poultice-boots made for that purpose (see Figs. 52 and 53).

These have an objection. They are apt to be allowed to get extremely dirty, and so, by carrying infective matter from the foot of one animal to that of another, undo the good that the warmth of the poultice is bringing about. The advantage of the ordinary sacking or canvas is that it may be cast aside after the application of each poultice. Where the boot is kept clean, however, it will save a great deal of time and trouble to the attendant.

While on the subject of poulticing, it is well to remark that in many cases it may be more advantageous to supply the necessary warmth and moisture to the foot by keeping it immersed in a narrow tub of water maintained at the required temperature. By this means the warmth is carried further up the limb (sometimes an important point), and the water can more conveniently be medicated with whatever is required than can the poultice. In fact, it is the author's general practice, where the attendants can be induced to take the necessary pains, to always advise this latter method.



Where a dressing is relied upon by some practitioners on account of the warmth it gives, others, even in identical cases, will depend upon the effects of cold. This may be applied by means of what are called 'swabs.' In their simplest form swabs may consist only of hay-bands or several layers of thick bandage bound round the foot and coronet, and kept cool by having water constantly poured upon them. In many cases the form of swab depicted in Fig. 54 will be found more convenient.

When only one foot is required to be dressed, and a water-supply is available, by far the preferable method is to attach one end of a length of rubber tubing to the water-tap, and fasten the other just above the coronet, allowing the water to trickle slowly over the foot. In cases where a forced water-supply is unobtainable, and the case warrants the extra trouble, much may be done with a medium-sized cask of water placed somewhere over the animal, and the rubber tubing connected with that.

Where the dressing is desired to be kept applied to the sole and frog only, there is no method more satisfactory than the shoe with plates.



The plates are of metal, preferably of thin sheet iron or zinc, and are slipped between the upper surface of the shoe and the foot after the manner shown in Fig. 55. The plates themselves are shaped as depicted in Fig. 55, a, b, c, a and b curved to meet the outlines of the shoe, and c shaped so as to wedge tightly over the posterior ends of the side plates, and between them and the shoe. A distinct advantage of the plate method of dressing is that a certain amount of pressure may be maintained on the sole and frog, a very important consideration in connection with some of the diseases with which we shall later deal.

When dealing with sinuous wounds of the foot, another favourite mode of applying dressings is by means of the syringe, and no better instrument for all cases can be found than that known as a quittor syringe (Fig. 56).

A further mode of applying dressing, and one frequently practised in connection with the foot, is known as 'plugging.' This is almost sufficiently indicated by its name. It consists in rolling portions of the dressing into little cylinders, wrapped round with thin paper, and introduced into a sinus or other position where considered necessary.

D. PLANTAR NEURECTOMY.

As a last resort in the treatment of many diseases of the foot the operation of neurectomy is often advised. It will be wise, therefore, to insert a description of the operation here.

Derivation of the Word.—For many years the operation was known simply as 'nerving' or 'unnerving,' and it was not until 1823, at the suggestion of Dr. George Pearson, that Percival introduced the word neurotomy to signify the operation with which we are now about to deal. The word neurotomy, however, used strictly, means the act or practice of dissection of nerves, and, when applied to the operation as practised to-day, describes only a step in the procedure.

As the operation really consists in cutting down upon, and afterwards excising a portion of the nerve, the modern appellation of neurectomy—from the Greek neuron, a nerve; and tome, a cutting, signifying the cutting out of a nerve or the portion of a nerve—is far more suitable.

According as the nerve operated on is the plantar or the median, the operation is known as plantar or median neurectomy.

History of the Operation.—It is to two English veterinarians that we owe the introduction of the operation to the veterinary world. In 1819 Professor Sewell announced himself as the originator of neurotomy. This claim was disputed by Moorcraft, who appears to have successfully shown himself to be the real person entitled to that honour, he having satisfactorily performed the operation on numerous animals for fully eighteen years prior to Professor Sewell's announcement. It appears that Moorcraft left this country for India in 1808, having practised the operation in more or less obscurity for some six or seven years previous to that. After his departure neurectomy, as introduced by him, either died away in repute, or was not made by him sufficiently public to become a matter of general knowledge. To Professor Sewell, therefore, although not the actual originator of the operation, belongs the honour of making it public to the veterinary profession.

In 1824, five years after Sewell's introduction, we find it practised on the Continent by Girard. We gather, however, from the writings of Percival and Liautard, that both in this country and on the Continent the operation was for several years largely in the stage of experiment. Unsuitable subjects were operated on; the work afterwards given to the animal improperly adjusted to his altered condition; and the bad after-results of the operation almost ignored by some, and greatly exaggerated by others. In fact, some long time elapsed before veterinary surgeons allotted to the operation that measure of credit which the results following it warranted.

The Object of the Operation is to render the foot insensitive to pain, and to give to an otherwise incurably lame animal a further period of usefulness. After the operation, as time goes on, this object may become defeated by the reunion of the divided ends of the nerve. In that case, neurectomy must necessarily be performed again.

The Operation.—Two forms of neurectomy are recognised—the high operation and the low. The low operation deals with the posterior digital branch of the plantar nerve, and the high operation with the plantar itself.

It is the latter operation with which we shall deal first. In our opinion it is that most likely to be followed by satisfactory results. The area supplied by the posterior digital is mainly the posterior portion of the digit. Thus, unless the cause of the lameness is diagnosed with certainty to be situated somewhere in the posterior region of the foot, section of the posterior digital alone will not give total insensibility to pain. Added to that, we may remember this: Below the point at which the digitals branch off from the plantar there is always more likelihood of the part we are attempting to render insensible being supplied by another and adventitious branch, or a branch that, as regards its direction, is abnormally distributed. As a last consideration, we may say that the higher operation is the easier to perform.

Percival, in his works on lameness, has some very sage remarks to make by way of a preliminary, and we cannot do better than quote them here. He says:

'To command success in neurectomy three considerations demand attention:

'1. The subject must be fit and proper; in particular, the disease for which neurectomy is performed should be suitable in kind, seat, stage, etc.

'2. The operation must be skilfully and effectually performed.

'3. The use that is made of the patient afterwards should not exceed what his altered condition appears to have fitted him for.

'The veterinarian who is guided by considerations such as those will find that he has restored to work horses who would otherwise have been utterly useless. A plain and safe argument wherewith to meet the objections to neurectomy is simply to ask the question what the animal is worth, or to what useful purpose he can be put, that happens to be the subject of such an operation.

'If the horse can be shown to be still serviceable and valuable, then he is not a legitimate subject for the operation. The rule of procedure I have laid down is to operate on no other but the incurably lame horse; and whenever this has been attended to, not only has success been the more brilliant, but indemnification from blame or reproach has been assured.'

Preparation of the Subject.—But little in the way of medicinal preparation is necessary. When the animal is a gross, heavy feeder, and carries a more than ordinary amount of cupboard, all that is needed is to withhold his usual allowance of food for some time prior to the operation, simply to avoid risk of rupture when casting. If considered advisable, a dose of physic may also be administered.

To the seat of operation, however, careful attention should be given. On the day previous to the operation the hair should be closely removed with the clipping machines, and the skin thoroughly cleansed with warm water and soap. After this, a bandage soaked in a 4 per cent, watery solution of carbolic acid should be wrapped lightly round the limb, and allowed to remain in position until the animal is cast and ready for the operation the following morning. On removing the bandage prior to operating, the part should again be bathed with a cold 5 per cent. solution of carbolic acid and swabbed dry. Attention to these details will serve to leave the wound in that favourable condition in which it heals nicely, and with the minimum amount of trouble.

Preliminary Steps.—By some practitioners the operation is performed with the animal standing, local anaesthesia having been first obtained by the use of cocaine, or an ethyl chloride spray. There is no gainsaying the fact, however, that the operation of neurectomy is a painful one, and that, with most operators, success will be more fully guaranteed with the animal cast and the limb held in a suitable position by an assistant.

The animal is thrown by the hobbles upon the side of the leg which is to be operated on. The cannon of the upper fore-limb is then fixed to the cannon of the upper hind, as described under the section of this chapter devoted to the methods of restraint, and the lower limb freed from the hobbles and drawn forward by an assistant by means of a stout piece of cord round the pastern.

An alternative method of holding the limb is to bind both fore-legs together above the knee by means of the side-line run round a few times in the form of the figure 8, and then fastened off. As in the former method, the lower foot is then removed from the hobble, and again held forward by an assistant. By either method the inside of the limb is operated on first.



Although it is not absolutely necessary, it is an advantage, especially to the inexperienced operator, to apply before operating an Esmarch's bandage and tourniquet (Fig. 57). This expels the greater part of the blood from the limb, and renders the operation comparatively bloodless.



The Esmarch bandage is composed of solid rubber, and with it the limb is bandaged tightly from below upwards. On reaching the knee the tourniquet is stretched round the limb, fastened by means of its buckle and strap, and the bandage removed. Those who feel they can dispense with the bandage use the tourniquet alone. For this purpose the form depicted in Fig. 58, and the one in general use at the Royal Veterinary College, is more suitable, on account of its wooden block, which may be placed so as to press on the main artery of supply.



Instruments Required.—These should be at hand in an earthenware or enamelled iron tray containing just sufficient of a 5 per cent. solution of carbolic acid to keep them covered. Those that are necessary will be a sharp scalpel, or, if preferred, one of the many forms of bistoury devised for the purpose (see Fig. 59), a pair of artery forceps, a needle ready threaded with silk or gut, one of the patterns of neurectomy needle (see Fig. 60), and a pair of blunt-pointed scissors curved on the flat. It is also an advantage, when once the incision through the skin is made, to employ one of the forms of elastic, self-adjusting tenacula (see Fig. 61) for keeping the edges of the wound apart while searching for the nerve.



Incision through the Skin.—We remember that the plantar nerve of the inner side is in close relation with the internal metacarpal artery, and that both, in company with the internal metacarpal vein, run down the limb in close proximity with the inner border of the flexor tendons. Also, we remember that the external plantar nerve has no attendant artery, although, like its fellow, it is to be found in close touch with the edge of the flexor tendons.

Bearing these landmarks in mind, we feel for the nerve in the hollow just above the fetlock-joint by noting the pulsations of the artery, and determining the edge of the flexor tendons. This done, a clean incision is made with the bistoury or the scalpel in the direction of the vessels. The incision should be made firmly and decisively, so that the skin may be cleanly penetrated with one clear cut. If judiciously made, little else in the shape of dissection will be needed.



It is now that the double tenaculum (Fig. 61) is applied. One clip is fixed to the anterior edge of the wound, and the other carried beneath the limb and made to grasp the posterior edge. If found desirable to keep the edges of the wound apart, and no tenaculum to hand, the same end may be accomplished by means of a needle and silk. In like manner as is the tenaculum, the silk is attached to one edge of the wound, carried under the limb, and firmly secured to the other.

Having made the incision, the wound should be wiped free from blood by means of a pledget of cotton-wool previously soaked in a carbolic acid solution and squeezed dry. At the bottom of the wound will now be seen the glistening white sheath, containing the vein, artery, and nerve. This should be picked up with the forceps, and a further incision made with the bistoury. Care should be exercised in making this second incision, or the artery may accidentally be opened. If an ordinary scalpel is used, the lower end of the sheath should be picked up and the point of the scalpel inserted through it. With the cutting edge of the scalpel turned towards the opening of the wound, the sheath is then slit from below upwards. The second incision satisfactorily made, the wound is again wiped dry, and the nerve seen as a piece of white, curled string in the posterior portion of the wound.

At this stage it is advisable to accurately ascertain whether what we have taken to be the nerve actually is it. This is done by taking it up with the forceps and giving it a sharp tweeze. A sudden struggle on the part of the patient will then leave no doubt in the operator's mind that it is the nerve he has interfered with.

Section of the Nerve.—The neurectomy needle (Fig. 60) is now taken, and, excluding the other structures, passed under the nerve. A piece of stout silk or ordinary string is then threaded through the eye of the needle, the needle withdrawn, and the silk left in position under the nerve. The silk is now tied in a loop, and the nerve by this means gently lifted from its bed. With the curved scissors or the scalpel it is severed as high up as is possible. The lower end of the severed nerve is then grasped firmly with the forceps, pulled downwards as far as possible, and then cut off. At least an inch of the nerve should be excised.

The animal is then turned over, and the opposite side of the limb operated on in the same manner.

The tourniquet is now removed, and the wound is examined for bleeding vessels. If the haemorrhage is only slight, the wound should be merely dabbed gently with the antiseptic wool until it has stayed. A larger vessel may be taken up with the artery forceps and ligatured, or the haemorrhage stopped by torsion. On no account, unless it it done to stay haemorrhage that is otherwise uncontrollable, should the wound be sutured with blood in it. With the wound once dry and clean, it is well to insert three or four silk sutures, but care must be taken not to draw them too tightly. This done, the patient may be allowed to get up. After-treatment.—This is simple. Over each wound is placed a pledget of antiseptic cotton-wool or tow, and the whole lightly covered with a bandage soaked in an antiseptic solution. For the first night the animal should be tied up short to the rack, and the following morning the bandages removed. A little boracic acid or iodoform, or a mixture of the two combined with starch (starch and boracic acid equal parts, iodoform 1 drachm to each ounce) should now be dusted over the wounds, the antiseptic pledgets renewed, and the bandage readjusted over all.

At the end of three or four days the bandages may be dispensed with. All that is necessary now is an occasional dusting with an antiseptic powder, and, as far as possible, the restriction of movement. At the end of a week the sutures may be removed, and the animal turned into a loose box or out to pasture.

E. MEDIAN NEURECTOMY.

As a palliative for lameness when confined to the foot, one would imagine that the plantar operation would be all sufficient. There are operators, however, who state that the results following section of the median nerve have been such as to cause them to entirely abandon the lower operation in its favour. If only for that reason a brief mention of the operation must be made here.

The operation was first performed in this country in October, 1895, the subject being one of the out-patients at the Royal Veterinary College Free Clinique.

For five or six years following this date Professor Hobday performed the operation some several hundred times, and was certainly instrumental in bringing the operation into prominence. Though so recently introduced here, it appears to have been practised for several years on the Continent, originating in Germany as early as 1867. In that country a first public account of it was published in 1885 by Professor Peters of Berlin, while in France it was introduced by Pellerin in 1892. In this operation a portion of the median nerve is excised on the inside of the elbow-joint just below the internal condyle of the humerus. Here the nerve runs behind the artery, then crosses it, and descends in a slightly forward direction behind the ridge formed by the radius.

The position of the limb most suitable for the operation is exactly that we have described as most convenient for the plantar excision. The animal is cast, preferably anaesthetized, and the limb removed from the hobbles, and held as far forward as is possible by an assistant with the side-line.

Professor Hobday's description of the operation is as follows:

'A bold incision is made through the skin and aponcurotic portion of the pectoralis transversus and panniculus muscles, about 1 to 3 inches (depending on the size of the horse) below the internal condyle of the humerus, and immediately behind the ridge formed by the radius. This latter, and the nerve which can be felt passing over the elbow-joint, form the chief landmarks. The haemorrhage which ensues is principally venous, and is easily controlled by the artery forceps. In some cases I have found it of advantage to put on a tourniquet below the seat of operation, but this is not always advisable, as it distends the radial artery. We now have exposed to view the glistening white fascia of the arm, which must be incised cautiously for about an inch. This will reveal the median nerve itself situated upon the red fibres of the flexor metacarpi internus muscle. If not fortunate enough to have cut immediately over the nerve, it can be readily felt with the finger between the belly of the flexor muscle and the radius.'[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. ix., p. 181.]

The nerve exposed, the remainder of the operation is exactly as that described in removing the portion of the nerve in the plantar operation. The wound is sutured and suitably dressed, and a fair amount of exercise afterwards allowed the patient.

F. LENGTH OF REST AFTER NEURECTOMY.

This is placed by the majority of surgeons at about three weeks to a month. Within that period no excessive exertion should be undergone by the patient. A certain amount of quiet exercise, however, is beneficial, facilitating the healing of the wounds, and accustoming the animal to the altered condition of his limb.

G. SEQUELAE OF NEURECTOMY.

These we shall relate collectively, making no distinction between those following excision of the plantar nerve and those succeeding section of the median. It must be remembered by the surgeon, however, that the unfortunate sequelae we are now about to describe are likely to be far more grave when following section of the larger nerve.

Liability of Pricked Foot going undetected.—On account of the warning they convey to the surgeon, first place among the sequelae of neurectomy must be given to accidents following loss of sensation. Take, for example, punctured foot. In any case, in the sense of being unforeseen, it is accidental. In the neurectomized foot it becomes doubly accidental, in that not only is it unforeseen, but that it is for some time indiscoverable. With the foot deprived of sensation, a nail may be picked up, or a prick sustained at the forge, and no intimation given to the attendant until pus has underrun the horn, and broken out at the coronet. What follows, then, is that the hoof as a whole, or the greater part of it, sloughs off.

No neurectomy should be undertaken unless this contingency has been allowed for. The owner should be advised of it by the surgeon, who should at the same time enjoin on his client the absolute necessity of giving to the neurectomized foot daily and careful attention.

Loss of Tone in the Non-sensitive Area.—In addition to the mischief resulting from a wound going undetected, it must be remembered that the loss of tone resulting from the operation gives to every wound (however slight), in the region supplied by the removed nerve, a sluggish and troublesome character. Difficult to deal with as wounds about the foot ordinarily are, they are rendered more so by a previous neurectomy.

Gelatinous Degeneration. This is a condition liable to occur in cases where the operation has been too long deferred, and when considerable structural alteration has already taken place in the shape of diseased bone or tendon, more especially in navicular disease. It consists in a peculiar softening of the structures of the limb, accompanied with enlargement, due to swelling of the connective tissues, the enlargement and softening generally making itself first apparent by a soft, pulpy swelling in the hollow of the heel.

From this onwards the enlargement increases, and lameness becomes excessive, the animal going more and more on his heels, until, finally, no portion of the solar surface of the foot comes to the ground at all.

The case is hopeless, and destruction should be advised.

Reported Case.—'The patient, a brown carriage gelding, was brought to the Royal Veterinary College infirmary in a cart on December 31, the only previous history obtainable being that it had suddenly fallen lame a month before.

'The symptoms presented were excessive lameness of the near fore-limb. On being trotted, the toe was elevated each time the foot reached the ground, progression being entirely on the heels. Separation of the hoof for about 2 inches at the hinder part of the coronet; oedematous swelling from foot to knee, extending during the next three days to the elbow. Great tenderness between the knee and the fetlock; below this no sensation whatever, as a pin was inserted in several places round the coronet without causing any symptoms of pain. On further examination, two unnerving scars were found. No treatment was adopted, and the horse was destroyed on January 6.

'On dissecting the leg, the following appearances presented themselves:

'The limb was very much enlarged, due to thickening of the connective tissue, the skin being removed only with difficulty. The tendons were soft and much thickened. A rupture of the skin at the coronet, just where the skin meets the wall of the foot. Large extravasations of blood at the back of the tendons, situated in the lower half. External nerve trunk had become reunited, at the point of junction there being a hard lump about the size of a walnut. Internal nerve trunk also had become reunited, and presented a thickened portion at the point of junction, but not so large as that of the outer side, and situated in the lower half of the tendon, about 2 inches higher than that on the external nerve. This nerve trunk was atrophied below the thickening, and had undergone gelatinous degeneration. Judging from the scars on the skin, this side had evidently been unnerved a week or ten days previously to that on the outer side. The band stretching across the back of the perforatus, between the external and internal nerves, appeared on the inside to have become firmly fixed into the tendon.

'On removing the hoof, under the sole there appeared a large quantity of very foetid pus; the laminae were very much inflamed in patches. There was an enormous thickening of connective tissues in the heel. On cutting longitudinally through the perforatus tendon, there was exposed a large blood-coloured mass, of a gelatinous appearance, situated on the perforatus tendon, the latter being very much thickened, and growing to the navicular bone. The underneath surface of the superior suspensory ligament was much thickened, and firmly adherent to the bone; at the posterior surface of the metacarpus there was a quantity of gelatinous substance. The anterior ligament of the fetlock-joint was thickened; the navicular bone was entire, but showed lesions of navicular disease, being ulcerated. Section through the bone did not reveal anything further. It may be here remarked that the ulcerations were on either side of the central ridge, and not at all on the ridge itself.

'Microscopic examination of the tissue joining the two ends of the nerve together revealed a few nerve fibres; the general appearance was that of granulation tissue, containing capillary vessels, which were fairly plentiful, and comparatively large in size.'[A]

[Footnote A: Veterinary Record, vol. iv., p. 386 (Hobday)]

Chronic Oedema of the Leg.—In some cases there is a distinct swelling of the leg some time after the operation. This exposes the limb to the infliction of sores from striking with the opposite foot, with, of course, the difficulty in healing we have just described.

Persistent Pruritus.—This annoying sequel occurs in the neurectomized limb, with or without gelatinous degeneration, and appears to be without a remedy. The itching in some cases is so intense as to lead the animal to constantly gnaw at the top of the foot. As one observer has remarked, the animal may begin literally biting pieces out of his limb. The result of the irritation and gnawing is fatal. Great sloughing of the parts takes place, and the animal has eventually to be slaughtered.

Fracture of the Bones.—The sudden loss of sensation in a foot may cause the animal to use violently the limb he has for months past been carefully nursing. It may be that the lameness for which the operation has been performed has been due to disease existing in the navicular bone, and extending, perhaps, to the os pedis. By the disease the bone has already been made brittle, its substance and ligamentous attachments perchance weakened and broken up by a slow-spreading caries, and rarefaction of the remaining bone substance rendered almost certain. In this instance, the free use of the foot, and the application to the diseased structures of an unwonted pressure immediately after the operation results in fracture. With the rupture of the structures we get the elevated toe and soft swelling in the heel, as described in gelatinous degeneration. Treatment, of course, is out of the question.

Neuroma.—A further sequel is the appearance at the seat of the operation of what is termed an 'amputational neuroma.' This is a tumour-like growth occurring on the end of the divided nerve. It is composed of connective-tissue elements permeated by nerve fibres which have grown out from the axis-cylinders of the nerve stump. It may vary in size from a pea to a hazel-nut, and is frequently the cause of much pain. This must be cut down upon and cleanly removed, taking away at the same time as much of the nerve as is possible.

Reunion of the Divided Nerve.—We may say at once that 'reunion' in the popular sense of the word does not take place. At a varying period after section, however, we do get a return of sensation. This is brought about in the following manner: The axis-cylinder of the nerve, still in connection with the spinal cord, swells somewhat, and hypertrophies. The cells of this hypertrophied portion show a great tendency to proliferate and produce new nerve structure. This growing point splits, and gives rise to several fibrils, which are new axis-cylinders. These commence to grow towards the periphery, and, in so doing, grow through the cicatricial tissue that has formed at the seat of the operation.

After passing through the cicatricial tissue (the amount of which tissue, of course, controls the length of time that insensibility remains), the growing axis-cylinders reach the degenerated portions of the nerve below the point of section. It is along the track of the old nerve that the new growths from the stump reproduce themselves.

The fact of the new growths having to pass through the fibrous tissue of the cicatrix before they can gain the course of the old nerve, along which latter their progress of growth is comparatively easy, affords ample illustration that as large a portion as is possible of the nerve should be removed when operating, in order to convey insensibility for the longest time. After reunion, of course, nothing remains but to repeat the operation.

The Existence of an Adventitious Nerve-supply.—While not exactly a sequel of the operation, the fact that it is not discovered until after the operation has been performed warrants us in mentioning it here. It is not an uncommon thing in the lower operation to find that sensation and symptoms of lameness still persist after section of the nerve. In many cases this has been traced to the existence of an abnormal nerve branch. In the higher operation this is not so likely to be met with. That it may occur, however, is shown by the following interesting case related by Harold Sessions, F.R.C.V.S.:[A]

[Footnote A: Journal of Comparative Pathology and Therapeutics, vol. xii., p. 343.]

'In June of 1898 I saw a hunter suffering from navicular disease. After carefully examining the leg, I advised the owner to have the operation of neurectomy performed upon him. This he decided to do, and the horse was sent to me about the beginning of July.



'The operation was performed in the ordinary way, without any difficulty whatever. The wounds healed nicely, but the horse still continued to go lame. Careful examination showed that there was still sensation on the outside of the foot. Thinking that possibly there might be two external metacarpal nerves, the horse was again cast, the operation being performed slightly lower down. Only the main branch of the external metacarpal nerve could be found. A piece of this was taken out, and the horse let up. On examination, sensation was still found in the posterior part of the outside of the foot. It was very evident that there was some abnormal distribution of the nerve, as sensation was still being conveyed to that part of the foot.

'As the horse was absolutely useless, and would have to be shot unless this piece of nerve could be found, he was again thrown, and after he had been anaesthetized I determined to follow the course of the nerve down, until I found where the accessory branch came from. This I found a little below the fetlock, about 1/2 inch below the point where the anterior plantar nerve is given off from the metacarpal nerve. It was about 1/2 inch below the spot where the anterior plantar nerve passes between the artery and vein of the foot, and it was somewhat difficult to get at it.

'Fig. 62 shows the exact size and distribution of the nerves. After the separation of the accessory branch, sensation was taken from the foot, and the horse went perfectly sound.'

Stumbling.—In addition to the sequelae we have mentioned, it is urged against the operation of neurectomy that one of the first effects of depriving the foot of the sense of touch is a tendency on the part of the animal to stumble. From the cases we have seen we cannot regard this objection as a serious one. Nevertheless, as veterinarians, with a knowledge of the physiology of the structures with which we are dealing, we must treat the objection with respect, for, after all, we are bound to allow that stumbling, and a bad form of it, would be but a natural sequence of the operation we have just performed. The real fact remains, however, that cases of stumbling, even immediately after the operation, are rare; and that even when they do occur, the animal seems easily able to accommodate himself to the altered condition, and as readily uses the comparatively inert mass at the end of his limb as he did previously the intact foot.

H. ADVANTAGES OF THE OPERATION.

From the prominence we have given to the unfortunate sequelae of the operation it might possibly be inferred that, while not giving it our absolute condemnation, we regard neurectomy with a certain amount of distrust. That we may contradict any such false impression, we state here that in many cases the operation is the only measure which will offer relief from pain, and restore to work an otherwise useless animal. In support of that we will now quote the recognised advantages of the operation.

That in many cases, when all other methods—surgical and medicinal—have failed, there is an immediate and total freedom from pain and lameness no one will deny. This, if it restores to active work an animal that would otherwise have had to have been cast aside, is ample justification for giving the operation, in spite of its many unfortunate terminations, a real place among the more highly favoured remedial measures to our hand.

'For Contracted Hoofs, viewing them in the light of idiopathic disease, or as being the immediate cause of the existing lameness in the uninflamed condition of the foot, and when consequential changes of its organism have taken place which bid defiance to therapeutic measures, neurotomy is a warrantable resource' (Percival).

'For Ringbone neurotomy has been practised with perfect success, after blistering and firing had both failed, notwithstanding the work the animal had to perform afterwards was of the most trying nature' (ibid.).

For Navicular Disease, when that malady is diagnosed, the earlier neurectomy is performed the better. The greater work given to the diseased bursa and bone, and the return of the contracted heels to the normal, brought about by the greater freedom with which the foot is used, are claimed by many to effect a cure.

Writing of navicular disease, and mentioning his belief in the possibility of the diseased bone effecting its own repair after the operation, Harold Leeney, M.R.C.V.S., says:

'The expansion of the heel, and rapid development of the frog (in this and many other cases) immediately after the operation, has not, I venture to think, attracted so much attention as it deserves, and may have something to do with those cases which appear to be actually cured, not merely made to go sound by absence of pain.'[A]

[Footnote A: Veterinary Record, vol. xi., p. 297.]

Speaking of the median operation before a meeting of the Central Veterinary Medical Society, Professor Hobday says:[A]

[Footnote A: Veterinary Record, vol. xiii., p. 427.]

'For old-standing lamenesses, when due to splints, exostoses, chronically sprained, thickened, and painful perforans and perforatus tendons, or cases of that kind which cause pain by pressing on the adjacent nerve structures, after all other known methods have failed, median neurectomy is the operation which will be most likely to give the animal a new lease of life and usefulness.'

'Of the Humanity and Utility of Neurectomy there can be no question whatever, and provided the cases are well selected, and the operation is efficiently performed, the advantages to be derived from it are most striking as well as enduring. But the disadvantages attending the loss of sensation in the foot have been brought forward on many occasions as an argument against neurectomy, and no one can deny that the foot with sensation is better than one without that faculty. But in a long experience of the operation I have never found these disadvantages outweigh the great advantages which have immediately followed it.'[A]

[Footnote A: Veterinary Journal, vol. ix., p. 178 (Fleming).]

Beyond these, the direct advantages of neurectomy, are other and more indirect advantages which claim attention.

The most astonishing among them is the fact noted by many writers of repute that exostoses (ringbones, side-bones, splints, etc.) rapidly diminish in size. This is vouched for by such well-known authorities as Zundel and Nocard.

Percival, too, mentions at some length the effect of the removal of pain on the oestral and generative functions, quoting a case of a brood cart-mare by reason of bony deposits being stayed from breeding for some years. Two months after the operation she went to work, and moved sound, her altered condition leading her to breed several healthy foals.

I. THE USE OF THE HORSE THAT HAS UNDERGONE NEURECTOMY.

No operation is of any considerable value to the veterinary surgeon unless he is able to show that after it he has left his patient workable. The alleviation of pain alone, commendable as it is from a humanitarian standpoint, is of no interest to the average owner of horse-flesh, unless with it he sees his animal capable of justifying his existence by the amount of labour performed.

Criticised in this way, is the operation of neurectomy justifiable? Upon that point the opinions of many practitioners, even at the present day, differ. We have already partly answered the objections likely to be raised on this score by stating that the work afterwards allotted the animal should be fixed to suit his altered condition. It may be taken as a general rule that in all cases where the animal's usefulness depends upon his delicacy of touch, as, for example, animals used solely for hacking or hunting, his future usefulness in that special sphere of work will be done away with.

Percival himself, always a strong advocate for the operation, fully recognises this. 'Does the neurotomized horse maintain the same step as before?' he asks. 'To this important question,' he replies, 'I unhesitatingly answer no; he does not. There can be no doubt but that the horse feels the ground upon which he is treading, and that he regulates his action in consonance with such feeling, so as to render his step the least jarring and fatiguing to himself, and therefore the easiest and pleasantest to his rider.... Such impressions'—those of touch—'being in the neurotomized subject, so far as regards the feeling of the foot, altogether wanting, a bold, fearless projection of the limb in action will be the consequence, followed by a putting down of the hoof flat upon the ground, as though it were a block, creating a sensation alike unpleasant both to horse and rider.'

Emphatic as Percival is upon this point, there are, nevertheless, others who maintain with equal stoutness that the unnerved animal is positively as safe, if not safer, than the animal who has not been so treated.

'That the tactile sense in the horse's foot is useful, it would be idle to deny; but that it is absolutely essential, even to safe progression, no one who has paid attention to the results of plantar neurectomy will maintain. On several occasions for years I have hunted, hacked, and driven horses which have been deprived of sensation in their fore-feet, and never had an accident with them. Their action has not been impaired by the operation; on the contrary, it has been vastly improved compared with what it had been previous to it. And my opinion has not been single in this respect, as many competent horsemen can give like evidence after long and severe trials of neurotomized horses. The opponents of neurotomy were, probably, not aware that there is in progression a muscular as well as a tactile sense.'

This latter contention is supported by numerous cases, reported at the time when the operation of neurectomy was at the heyday of its popularity. Two I select from writings of a later period:

Recorded Cases.—1. 'Two of the finest among the many fine horses in the Second Life Guards were so lame from navicular disease, when I joined the regiment, that they were unsafe and unsightly to ride, and were therefore entered on the list to be cast off and sold. One was so crippled that it could scarcely be moved out of its stable. Peeling sorry at having to get rid of such good horses, and anxious to give another blow to the mistaken theory that unnerved animals were unsafe, I obtained the consent of my commanding officer, who patronizes practical conclusions, to perform neurotomy. This was carried out on both horses about eighteen months ago. Within a fortnight they were at their duty, absolutely free from lameness, and with first-rate action, and one of them, from being troublesome and unsteady in the ranks—probably from the pain in its feet—had become quite steady and tractable. Instead of being lame, blundering, and unsafe, both were sound, free in movement, and secure, and, the pain being abolished, they looked improved in condition.

'During the month of July the regiment attended the summer drills at Aldershot, and five days every week for a month these horses carried a weight of about 22 stones each over the roughest and most dangerous ground, nearly always at a fast pace, and for four, five, or six hours each day; and yet they never fell or blundered, and the troopers who rode them had unbounded confidence in their sure-footedness. They returned to Windsor, at the end of the month's severe test, as sound in their paces as when they left, and certainly now offer no indication whatever that they are less safe to ride than any other horse in the regiment. The effects of the relief from pain are also most marked, not only in the altered gait out of doors, but also in the stable.'[A]

[Footnote A: Veterinary Journal, vol. ix., p. 178 (George Fleming, F.B.C.V.S.).]

2. 'Some years ago I operated upon a valuable hunter, the property of a gentleman in Kildare, the animal having shown unmistakable symptoms of navicular disease for some months previously, and which had been unsuccessfully combated by the milder forms of treatment for the disease without any benefit. Although the horse went sound, the owner feared to ride him, and sent him to be sold in Dublin, where he was disposed of for a small price, and I then lost sight of him. The following Punchestown Races, to my surprise, amongst a group of horses walking round the paddock previous to saddling for an important race, I recognised my old patient, bandaged, clothed, and trained, ready to take his part in the cross-country contest, and surrounded by a host of admirers willing to back him at any price.

'Having satisfied myself that it was no other than the same animal, my first impulse was at once to find out the jockey who was to ride him, and warn him of his danger by telling him his mount was devoid of feeling in both fore-feet; but the saddling-bell had already rung, and in a few moments more the jockey emerged from the weighing-room and the next view of the horse was his tearing up the course in the preliminary, and "pulling double." I was sorry for the jockey if he felt as I did at that moment, for if he did I fear he and his horse would have parted company at the first fence, as I was certain there would be a smash before the end of the long and difficult three miles of the Kildare Hunt Cup course. It was not until I saw him again in the front rank passing the stand, in the first round, that I breathed freely, and even then I felt very guilty, and, had he come to grief badly, I don't think I should ever have operated on another horse except in such a way as would have left unmistakable traces after it.

'"The old horse wins!" screamed a thousand voices as the competitors safely cleared the last bank (now taken away for a gorse fence) the last time round, and from that moment the operation went up in my estimation a hundredfold, and I almost lost all interest in the finish (and it was a close one, with my patient a good third), resolving I would operate for the future on every animal, young and old, which showed symptoms of navicular disease.

'Neither owner nor jockey knew the horse had been operated on, and he was soon after, on the strength of his performance, sold for a good price to come to England. It is idle to think that all cases are as successful as this was, as experience soon told me; but I consider that, in careful hands, the advantages well outweigh the disadvantages of the operation, and I have selected this instance merely as a practical example.'[A]

[Footnote A: Veterinary Journal, vol. iii., p. 254 (W. Pallin, M.B.C.V.S.).]

It is solely with the object of ventilating both sides of the question that we quote the last two cases. In our opinion, the colours in which the results of the operation are there painted are far too rosy. The practitioner who has before him the task of satisfying a client as to what will or what will not be the results of an operation he has suggested will do well to weigh each side of the argument carefully, and endeavour in his explanation to strike the happy mean.

We hold, further, that the animal who has previously been accustomed to fast work, and to work entailing a large call upon the sense of touch when passing over rough and uneven ground, will be far more likely, in his neurectomized condition, to give satisfaction to his owner if put to a slower and a more suitable means of earning his living.



CHAPTER VI

FAULTY CONFORMATION

Under this heading we shall deal with such formations of the feet as depart sufficiently from the normal to render them serious. Faulty conformation may be either congenital or acquired, and acquired gradually as the result of slowly operating causes, or suddenly as the sequel to previous acute disease. Whether congenital or acquired, serious in its nature or comparatively of no account, the veterinary surgeon will often find that the matter of conformation is one which will have a direct bearing on many of his 'foot' cases, and, furthermore, that it is one upon which he will often be called to give advice.

A. WEAK HEELS.

Definition.—That condition of the wall in which, owing to the softness of the horn and the oblique direction of the horn fibres, the heels are unable properly to bear the body-weight, and, as a consequence, curve in beneath the sole. We give the condition first mention, not because of its greater importance, but for the reason that it is frequently the forerunner of the condition to be next described—namely, contracted feet.

Symptoms.—The extreme point of the heel is not affected unless the foot has been greatly neglected, and the condition allowed to develop. Where, however, the foot has been uncared for, curving in of the wall takes place to an alarming degree, and the heels curl underneath the foot to such an extent as to grow over the sole and the bars. By the pressure they exert on the sole corns result, and the animal is lamed.

Causes.—In the main this defect is hereditary. It is seen commonly in connection with flat-foot, and where the horn of the wall is thin and shelly.

Treatment.—In the case of weak or 'turned in' heels no suitable bearing is offered for the shoe in the posterior half of the foot. Any attempt to induce the heels to bear weight is immediately followed by their bending in. It follows from this that the best shoe to be used here is one in which the bearing is confined to the anterior half of the wall, the heels being relieved by being sufficiently pared. As might be expected, this bearing on the anterior half only of the foot is insufficient; pressure must be given the frog. This latter end is best gained by a bar shoe (Fig. 68). With it the anterior portions of the wall, the whole of the bars, and the whole of the frog may be in contact, and the heels only so pared as to take no bearing at all. A few such shoeings sees the defect remedied. In every instance paring of the sole should be discouraged, as it serves but to increase the deformity.

B. CONTRACTED FOOT.

(a) GENERAL CONTRACTION—CONTRACTED HEELS.

Definition. By the term contracted foot, otherwise known as hoof-bound, is indicated a condition in which the foot, more especially the posterior half of it, is, or becomes, narrower from side to side than is normal.

It must be borne in mind, however, that certain breeds of horses have normally a foot which nearer approaches the oval than the circular in form, and that a narrow foot is not necessarily a contracted foot.

The contraction may be bilateral when affecting both heels of the same foot and extending to the quarters, or unilateral when the inside or outside heel only is affected.

In some cases contraction is confined to one foot, while in others it may be noticed equally bad in both. It is a matter of common knowledge that contraction is usually seen in the fore-feet, while the hind seldom or never suffer from it, a fact which, to our minds, seems difficult of adequate explanation. Zundel explains this by stating that contraction is principally observed in the fore-feet, by reason of the fact that when lameness arises from it alteration in action will more readily be detected in front than behind. Percival, on the other hand, suggests that the greater expansive powers of the hind-foot, by reason of the impetus of its action, is able to overcome any influence operating towards contraction. It may be, however, that given a cause for contraction, such as the removal of the frog's counter-pressure with the ground by faulty shoeing or excessive paring, the fore-feet, by reason of their being called upon to bear the greater part of the body-weight, are the first to suffer.

Flat feet with weak heels are those most frequently affected, and, as we have already intimated, the condition may exist with or without other disease of the foot.

Depending upon its degree, contracted foot may vary from a simple abnormality, non-inflammatory and painless, to a condition in which it becomes a veritable disease, giving rise to a bad form of lameness, and bringing about a withered and sometimes discharging and cankerous affection of the frog.

Symptoms.—In its early stages contraction is difficult of detection, and where both feet are affected may for some time go unsuspected. With only one foot undergoing change, the early stages may the more readily be marked, for in this case comparison with the other and sound foot will at once reveal the alteration in shape. If lameness in the suspected foot is present, then any lingering doubt will be quickly dispelled.

When far advanced, contraction offers signs that cannot well be missed. The converging of the heels narrows the V-shaped indentation in the sole for the reception of the frog. As a consequence of this, the frog itself becomes atrophied by reason of the continual pressure exerted upon it by the ingrowing horn of the wall and the bars. The median and lateral lacunae of this organ, from being fairly broad and open channels, become pressed into mere crack-like openings (see the commencing of this condition in Fig. 80, and a badly wasted frog in Fig. 74A). As the case goes on, the lateral branches of the frog entirely disappear, and all that is left of the organ is a remnant of its body or cushion, now wedged in tightly between the bars. Following upon the disappearance of the frog, we find that the bars are in contact, or, in some cases, actually overlapping each other at their posterior extremities.

At this stage, perhaps, the whole condition has become aggravated by a foul discharge from the place originally occupied by the frog, and the foot, especially in the region of the heels, has become hot and tender—really a form of local and subacute laminitis.

The long-continued inflammation, although only of a low type, renders the horn of the hoof hard and dry, and only with difficulty will the ordinary foot instruments cut it. This in its turn leads to cracks and fissures in various places, but more especially in the bars and what is left of the frog. Often, too, cracks will appear in the horn of the quarters, and a troublesome and incurable form of sand-crack results.