Chapter 56

This usually sets in with swelling, heat, and tenderness of the hollow of the heel, with erections of the hairs and redness (in white skins), with stiffness and lameness, which may be extreme in irritable horses. Soon slight cracks appear transversely, and may gain in depth and width, and may even suppurate. More frequently they become covered at the edges or throughout by firm incrustations resulting from the drying of the liquids thrown out, and the skin becomes increasingly thick and rigid. A similar condition occurs behind the knee and in front of the hock (malanders and salanders), and may extend from these points to the hoof, virtually incasing that side of the limb in a permanent incrusting sheath.

_Causes._--Besides a heavy lymphatic constitution, which predisposes to this affection, the causes are overfeeding on grain, unwholesome fodder, close, hot, dirty stables, constant contact with dung and urine and their emanations, working in deep, irritant mud; above all, in limestone districts, irritation by dry limestones or sandy dust in dry weather on dirt roads; also cold drafts, snow, and freezing mud, washing the legs with caustic soap, wrapping the wet legs in thick woolen bandages which soak the skin and render it sensitive when exposed next day, clipping the heels, weak heart and circulation, natural or supervening on overwork, imperfect nourishment, impure air, lack of sunshine, chronic exhausting, or debilitating diseases, or functional or structural diseases of the heart, liver, or kidneys. These last induce dropsical swelling of the limbs (stocking), weaken the parts, and induce cracking. Finally the cicatrix of a preexisting crack, weak, rigid, and unyielding, is liable to reopen under any severe exertion; hence rapid paces and heavy draft are active causes.

_Treatment._--In treatment the first step is to ascertain and remove the cause whenever possible. If there is much local heat and inflammation, a laxative (5 drams aloes or 1 pound Glauber's salt) may be given, and for the pampered animal the grain should be reduced or replaced altogether by bran mashes, flaxseed, and other laxative, nonstimulating feed. In the debilitated, on the other hand, nutritious food and bitter tonics may be given, and even a course of arsenic (5 grains arsenic with 1 dram bicarbonate of soda daily). When the legs swell, exercise on dry roads, hand rubbing, and evenly applied bandages are good, and mild astringents, like extract of witch-hazel, may be applied and the part subsequently rubbed dry and bandaged. If there is much heat but unbroken skin, a lotion of 2 drams sugar of lead to 1 quart of water may be applied on a thin bandage, covered in cold weather with a dry one. The same may be used after the cracks appear, or a solution of sulphurous acid 1 part, glycerin 1 part, and water 1 part, applied on cotton and well covered by a bandage. In case these should prove unsuitable to the particular case, the part may be smeared with vaseline 1 ounce, sugar of lead 1 dram, and carbolic acid 10 drops.

INFLAMMATION OF THE HEELS WITH SEBACEOUS SECRETION (GREASE, OR CANKER).

This is a specific affection of the heels of horses usually associated with the growth of a parasitic fungus, an offensive discharge from the numerous sebaceous glands, and, in bad cases, the formation of red, raw excrescences (grapes) from the surface. It is to be distinguished (1) from simple inflammation in which the special fetid discharge and the tendency to the formation of "grapes" are absent; (2) from horsepox, in which the abundant exudate forms a firm, yellow incrustation around the roots of the hair, and is embedded at intervals in the pits formed by the individual pocks, and in which there is no vascular excrescence; (3) from foot scabies (mange), in which the presence of an acarus is distinctive; (4) from lymphangitis, in which the swelling appears suddenly, extending around the entire limb as high as the hock, and on the inner side of the thigh along the line of the vein to the groin, and in which there is active fever, and (5) from erysipelas, in which there is active fever (wanting in grease), the implication of the deeper layers of the skin and of the parts beneath giving a boggy feeling to the parts, the absence of the fetid, greasy discharge, and finally a tendency to form pus loosely in the tissues without any limiting membrane, as in abscess. Another distinctive feature of grease is its tendency to implicate the skin which secretes the bulbs or heels of the horny frog and in the cleft of the frog, constituting the disease known as canker.

_Causes._--The predisposing causes of grease are essentially the same as those of simple inflammation of the heel, so that the reader may consult the preceding section. Though a specific fungus and bacteria of different kinds are present, they tend mainly to aggravation of the disease, and are not proved to be essential factors in causation.

_Symptoms._--The symptoms vary according to whether the disease comes on suddenly or more tardily. In the first case there is a sudden swelling of the skin in the heel, with heat, tenderness, itching, and stiffness, which is lessened during exercise. In the slower forms there is seen only a slight swelling after rest, and with little heat or inflammation for a week or more. Even at this early stage, a slight, serous oozing may be detected. As the swelling increases, extending up toward the hock or knees, the hairs stand erect, and are bedewed by moisture no longer clear and odorless, but grayish, milky, and fetid. The fetor of the discharge draws attention to the part whenever one enters the stable, and the swollen pastern and wet, matted hairs on the heel draw attention to the seat of the malady. If actively treated, the disease may not advance further, but if neglected the tense, tender skin cracks open, leaving open sores from which vascular bleeding growths grow up, constituting the "grapes." The hair is shed, and the heel may appear but as one mass of rounded, red, angry excrescences which bleed on handling and are covered with the now repulsively fetid, decomposing discharge. During this time there is little or no fever, the animal feeds well, and but for its local trouble it might continue at work. When the malady extends to the frog, there is a fetid discharge from its cleft or from the depressions at its sides, and this gradually extends to its whole surface and upon the adjacent parts of the sole. The horn meanwhile becomes soft, whitish, and fleshy in aspect, its constituent tubes being greatly enlarged and losing their natural cohesion; it grows rapidly above the level of the surrounding horn, and when pared is found to be penetrated to an unusual depth by the secreting papillæ, and that at intervals these have bulged out into a vascular fungous mass comparable to the "grapes."

_Treatment._--In treatment hygienic measures occupy a front rank, but are in themselves insufficient to establish a cure. All local and general conditions which favor the production and persistence of the disease must be guarded against. Above all, cleanliness and purity of the stable and air must be obtained; also nourishing diet, regular exercise, and the avoidance of local irritants--septic, muddy, chilling, etc. At the outset benzoated oxid of zinc ointment may be used with advantage. A still better dressing is made with 1 ounce vaseline, 2 drams oxid of zinc, and 20 drops iodized phenol. If the surface is much swollen and tender, a flaxseed poultice may be applied, over the surface of which has been poured some of the following lotion: Sugar of lead, one-half ounce; carbolic acid, 1 dram; water, 1 quart. All the astringents of the pharmacopoeia have been employed with more or less advantage, and some particular one seems to suit particular cases or patients. To destroy the grapes, they may be rubbed daily with strong caustics (copperas, bluestone, lunar caustic), or each may be tied round its neck with a stout, waxed thread, or, finally and more speedily, they may be cut off by a black-smith's shovel heated to redness and applied with its sharp edge toward the neck of the excrescence, over a cold shovel held between it and the skin to protect the skin from the heat. The cold shovel must be kept cool by frequent dipping in water. After the removal of the grapes the astringent dressing must be persistently applied to the surface. When the frog is affected, it must be pared to the quick and dressed with dry caustic powders (quicklime, copperas, bluestone) or carbolic acid and subjected to pressure, the dressing being renewed every day at least.

ERYSIPELAS.

This is a specific contagious disease, characterized by spreading, dropsical inflammation of the skin and subcutaneous tissues, attended with general fever. It differs from most specific diseases in the absence of a definite period of incubation, a regular course and duration, and a conferring of immunity on the subject after recovery. On the contrary, one attack of erysipelas predisposes to another, partly, doubtless, by the loss of tone and vitality in the affected tissues, but also, perhaps, because of the survival of the infecting germ.

_Cause._--It is no longer to be doubted that the microbes found in the inflammatory product are the true cause of erysipelas, as by their means the disease can be successfully transferred from man to animals and from one animal to another. This transition may be direct or through the medium of infected buildings or other articles. Yet from the varying severity of erysipelas in different outbreaks and localities it has been surmised that various different microbes are operative in this disease, and a perfect knowledge of them might perhaps enable us to divide erysipelas into two or more distinct affections. At present we must recognize it as a specific inflammation due to a bacterial poison and closely allied to septicemia. Erysipelas was formerly known as surgical when it spread from a wound (through which the germ had gained access) and medical, or idiopathic, when it started independently of any recognizable lesion. Depending as it does, however, upon a germ distinct from the body, the disease must be looked upon as such, no matter by what channel the germ found an entrance. Erysipelas which follows a wound is usually much more violent than the other form, the difference being doubtless partly due to the lowered vitality of the wounded tissues and to the oxidation and septic changes which are invited on the raw, exposed surface. As apparently idiopathic cases may be due to infection through bites of insects, the small amount of poison inserted may serve to moderate the violence.

This affection may attack a wound on any part of the horse's body, while, apart from wounds, it is most frequent about the head and the hind limbs. It is to be distinguished from ordinary inflammations by its gradual extension from the point first attacked, by the abundant liquid exudation into the affected part, by the tension of the skin over the affected part, by its soft, boggy feeling, allowing it to be deeply indented by the finger, by the abrupt line of limitation between the diseased and the healthy skin, the former descending suddenly to the healthy level instead of shading off slowly toward it, by the tendency of the inflammation to extend deeply into the subjacent tissues and into the muscles and other structures, by the great tendency to death and sloughing of portions of skin and of the structures beneath, by the formation of pus at various different points throughout the diseased parts without any surrounding sac to protect the surrounding structures from its destructive action, and without the usual disposition of pus to advance harmlessly toward the surface and escape; and, finally, by a low, prostrating type of fever, with elevated temperature of the body, coated tongue, excited breathing, and loss of appetite. The pus when escaping through a lancet wound is grayish, brownish, or reddish, with a heavy or fetid odor, and inter-mixed with shreds of broken-down tissues. The most destructive form, however, is that in which pus is deficient and gangrene and sloughing more speedy and extensive.

_Treatment_ resolves itself mainly into the elimination from the system of the poisonous products of the bacteria by laxatives and diuretics, the sustaining of the failing vitality by tonics and stimulants, above all those of the nature of antiferments, and the local application of astringent and antiseptic agents. Internal treatment may consist in 4 drams tincture of muriate of iron and one-half dram muriate of ammonia or chlorate of potash, given in a pint of water every two hours. To this may be added, liberally, whisky or brandy when the prostration is very marked. Locally a strong solution of iron, alum, or of sulphate of iron and laudanum may be used; or the affected part may be painted with tincture of muriate of iron or with iodized phenol. In mild cases a lotion of 4 drams sugar of lead and 2 ounces laudanum in a quart of water may be applied. It is desirable to avoid the formation of wounds and the consequent septic action, yet when pus has formed and is felt by fluctuation under the finger to be approaching the surface it should be freely opened with a clean, sharp lancet, and the wound thereafter disinfected daily with carbolic acid 1 part to water 10 parts, with a saturated solution of hyposulphite of soda, or with powders of iodoform or salol.

HORSEPOX, ANTHRAX, AND CUTANEOUS GLANDERS (FARCY).

These subjects are discussed under the head of contagious diseases.

CALLOSITIES.

These are simple thickening and induration of the cuticle by reason of continued pressure, notably in lying down on a hard surface. Being devoid of hair, they cause blemishes; hence, smooth floors and good bedding should be provided as preventives.

HORNY SLOUGHS (SITFASTS), OR SLOUGHING CALLOSITIES.

These are circumscribed sloughs of limited portions of the skin, the result of pressure by badly fitting harness or by irritating masses of dirt, sweat, and hairs under the harness. They are most common under the saddle, but may be found under collar or breeching as well. The sitfast is a piece of dead tissue which would be thrown off but that it has formed firm connections with the fibrous skin beneath, or even deeper with the fibrous layers (fascia) of the muscles, or with the bones, and is thus bound in its place as a persistent source of irritation. The hornlike slough may thus involve the superficial part of the skin only, or the whole thickness of the skin, and even of some of the structures beneath. The first object is to remove the dead irritant by dissecting it off with a sharp knife, after which the sore may be treated with simple wet cloths or a weak carbolic-acid lotion, like a common wound. If the outline of the dead mass is too indefinite, a linseed-meal poultice will make its outline more evident to the operator. If the fascia or bone has become gangrenous, the dead portion must be removed with the hornlike skin. During and after treatment the horse must be kept at rest or the harness must be so adjusted that no pressure can come near the affected parts. (See also page 496.)

WARTS.

These are essentially a morbid overgrowth of the superficial papillary layer of the skin and of the investing cuticular layer. They are mostly seen in young horses, about the lips, eyelids, cheeks, ears, beneath the belly, and on the sheath, but may develop anywhere. The smaller ones may be clipped off with scissors and the raw surface cauterized with bluestone. The larger may be sliced off with a sharp knife, or if with a narrow neck they may be twisted off and then cauterized. If very vascular they may be strangled by a wax thread or cord tied around their necks, at least three turns being made around and the ends being fixed by passing them beneath the last preceding turn of the cord, so that they can be tightened day by day as they slacken by shrinkage of the tissues. If the neck is too broad it may be transfixed several times with a double-threaded needle and then be tied in sections. Very broad warts that can not be treated in this way may be burned down with a soldering bolt at a red heat to beneath the surface of the skin, and any subsequent tendency to overgrowth kept down by bluestone.

BLACK PIGMENT TUMORS, OR MELANOSIS.

These are common in gray and in white horses on the naturally black parts of the skin at the roots of the tail, around the anus, vulva, udder, sheath, eyelids, and lips. They are readily recognized by their inky-black color, which extends throughout the whole mass. They may appear as simple, pealike masses, or as multiple tumors aggregating many pounds, especially around the tail. In the horse these are usually simple tumors, and may be removed with the knife. In exceptional cases they prove cancerous, as they usually are in man.

EPITHELIAL CANCER, OR EPITHELIOMA.

This sometimes occurs on the lips at the angle of the mouth and elsewhere in the horse. It begins as a small, wartlike tumor, which grows slowly at first, but finally bursts open, ulcerates, and extends laterally and deeply in the skin and other tissues, destroying them as it advances (rodent ulcer). It is made up of a fibrous framework and numerous round, ovoid, or cylindrical cavities, lined with masses of epithelial cells, which may be squeezed out as a fetid, caseous material. Early and thorough removal with the knife is the most successful treatment.

VEGETABLE PARASITES OF THE SKIN.

(Pl. XXXVIII, figs. 2, 3, 4.)

PARASITE: _Trichophyton tonsurans._ MALADY: _Tinea tonsurans, or circinate ringworm._--This is especially common in young horses coming into training and work, in low-conditioned colts in winter and spring after confinement indoors, during molting, in lymphatic rather than nervous subjects, and at the same time in several animals that have herded together. The disease is common to man, and among the domestic animals to horse, ox, goat, dog, cat, and in rare instances to sheep and swine. Hence it is common to find animals of different species and their attendants suffering at once, the diseases having been propagated from one to the other.

_Symptoms._--In the horse the symptoms are the formation of a circular, scurfy patch where the fungus has established itself, the hairs of the affected spot being erect, bristly, twisted, broken, or split up and dropping off. Later the spot first affected has become entirely bald, and a circular row of hairs around this are erect, bristly, broken, and split. These in turn are shed and a new row outside passes through the same process, so that the extension is made in more or less circular outline. The central bald spot, covered with a grayish scurf and surrounded by a circle of broken and split hairs, is characteristic. If the scurf and diseased hairs are treated with caustic-potash solution and put under the microscope, the natural cells of the cuticle and hair will be seen to have become transparent, while the groups of spherical cells and branching filaments of the fungus stand out prominently in the substance of both, dark and unchanged. The eruption usually appears on the back, loins, croup, chest, and head. It tends to spontaneous recovery in a month or two, leaving for a time a dappled coat from the spots of short, light-colored hair of the new growth.

The most effective way of reaching the parasite in the hair follicles is to extract the hairs individually, but in the horse the mere shaving of the affected part is usually enough. It may then be painted with tincture of iodin twice a day for two weeks. Germs about the stable may be covered up or destroyed by a whitewash of freshly burned quicklime, the harness, brushes, etc., may be washed with caustic soda, and then smeared with a solution of corrosive sublimate one-half dram and water 1 pint. The clothing may be boiled and dried.

PARASITE: _Achorion schönleini._ MALADY: _Favus, or honeycomb ringworm._--Mégnin and Goyau, who describe this in the horse, say that it loses its characteristic honeycomb or cup-shaped appearance, and forms only a series of closely aggregated, dry, yellowish crusts the size of hemp seed on the trunk, shoulders, flanks, or thighs. They are accompanied by severe itching, especially at night. The cryptogam, formed of spherical cells with a few filaments only, grows in the hair follicles and on the cuticle, and thus a crust often forms around the root of a hair. Like the other cryptogams, their color, as seen under the microscope, is unaffected by acetic acid, alcohol, ether, or oil of turpentine, while the cells are turned bluish by iodin. For treatment, remove the hair and apply tincture of iodin or corrosive sublimate lotion, as advised under the last paragraph.

PARASITE: _Microsporon furfur._ MALADY: _Parasitic pityriasis._--This attacks the horse's head where the harness presses, and leads to dropping of the hair, leaving bald patches covered with a branlike scurf, without any eruption, heat, tenderness, swelling, or rigidity of the skin. A lotion of carbolic acid 1 dram and water 2-1/2 ounces is usually applied to effect a cure.

ANIMAL PARASITES OF THE SKIN.[6]

ACARIASIS, OR MANGE.

This affection is due to the irritation of the skin caused by the presence of nearly microscopic acari, or mites. The disease varies, however, according to the species of acarus which infests the skin, so that we must treat of several different kinds of acariasis.

PARASITE: _Sarcoptes scabiei equi._ MALADY: _Sarcoptic acariasis._--This is the special _Sarcoptes_ of the horse, but under favorable conditions it can be transmitted to ass and mule, and even to man, and may live indefinitely on the human skin. The mite (Pl. XXXIX, fig. 1) is nearly microscopical, but may be detected with a magnifying lens among moving scurf taken from the infected skin. Like all _Sarcoptes_, it burrows little galleries in and beneath the scurf skin, where it hides and lays its eggs and where its young are hatched. It is therefore often difficult to find the parasite on the surface, unless the skin has been heated by a temporary exposure to the sun or in a warm room. The mite may be detected more readily by placing scrapings on black cardboard and warming, or better by macerating scabs or scrapings in a solution of caustic soda or potash and then examining them microscopically. Like other acari, this is wonderfully prolific, a new generation of fifteen individuals being possible every fifteen days, so that in three months the offspring of a single pair may produce generations aggregating 1,500,000 young. The _Sarcoptes_ have less vitality than the nonburrowing acari, as they die in an hour when kept apart from the skin in dry air at a heat of 145° F. They live 12 to 14 days apart from the skin in the damp air of a stable. On a piece of damp hide they lived till the twenty-fourth day, when they began to die, and all were dead on the twenty-eighth.

_Symptoms._--The symptoms are an incessant, intolerable, and increasing itching of some part of the skin (head, mane, tail, back, etc.), the horse inclining himself toward the hand that scratches him, and moving his lips as if himself scratching. The hairs may be broken and rubbed off, but the part is never entirely bald, as in ringworm, and there may be papules or any kind of eruption or open sores from the energy of the scratching. Scabs of any thickness may form, but the special features are the intense itching and the presence of the acarus.