Part 56 (1/2)
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 appet.i.te. 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.
h.o.r.n.y SLOUGHS (SITFASTS), OR SLOUGHING CALLOSITIES.
These are circ.u.mscribed sloughs of limited portions of the skin, the result of pressure by badly fitting harness or by irritating ma.s.ses 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 ma.s.s 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 pa.s.sing 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 a.n.u.s, v.u.l.v.a, udder, sheath, eyelids, and lips. They are readily recognized by their inky-black color, which extends throughout the whole ma.s.s. They may appear as simple, pealike ma.s.ses, 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 ma.s.ses 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. x.x.xVIII, 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 pa.s.ses 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 schonleini._ MALADY: _Favus, or honeycomb ringworm._--Megnin 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.