DISEASES OF THE SKIN.

By M. R. Trumbower, D. V. S.

[Revised by John R. Mohler, V. M. D.]

GENERAL DISCUSSION.

The skin consists of two parts—a superficial layer, the epidermis, or cuticle, and the deep, or true, skin, the dermis, cutis vera, or corium.

The epidermis, cuticle, or scarf skin, is an epithelial structure, forming a protective covering to the corium. It varies in thickness, is quite insensible and nonvascular, and consists of a sheet of cells.

The epidermis is divided into a firm and transparent superficial and a deep, soft layer. The latter is the rete mucosum, whose cells contain the pigment which gives color to the skin. The deep surface of the epidermis is accurately molded on the papillary layer of the true skin, and, when removed by maceration, presents depressions which correspond to the elevations on the dermis. From the cuticle tubular prolongations pass into the sebaceous and sudorific glands; thus the entire surface of the body is inclosed by the cuticle.

The dermis, or true skin, is vascular and highly sensitive, containing the tactile ends of the nerves of touch. It is covered by epidermis and attached to the underlying parts by a layer of areolar tissue, which usually contains fat. The cutis consists of a fibro-areolar tissue and vessels of supply. It is divided into two layers, the deep, or true, corium and the upper, or papillary. The corium consists of strong interlacing fibrous bands, chiefly white; its meshes are larger and more open toward the attached surface, giving lodgment to the sweat glands and fat. The papillary, or superficial, layer is formed of a series of small conical eminences or papillæ, which are highly sensitive, and consists of a homogenous, transparent tissue. The blood vessels form dense capillary plexuses in the corium, terminating by loops in the papillæ. The papillary nerves run in a waving manner, usually terminating in loops.

Hair is an appendage of the skin and forms its external covering. It is a special modification of epidermis, having the same essential structure, and consists of a root, shaft, and point. The root has a bulbous extremity, is lighter and softer than the stem, and is lodged in a recess or hair follicle, which may either be in the corium or subcutaneous areolæ. The follicle is dilated at the bottom to correspond to the root bulb, and the ducts of one or more sebaceous glands open into it. At the bottom of each follicle is a conical, vascular papilla, similar in every respect to those on the surface of the dermis; this papilla fits into a corresponding depression in the root of the hair. The shaft consists of a center, or medulla, a surrounding fibrous portion, and an external coating, or cortex. The medulla consists of cells containing pigment or fat, is opaque, and deeply colored. All kinds of hair do not have this medulla. The fibrous portion occupies the bulk of the stem, and the cortex is merely a single layer of thin, flat, imbricated (shinglelike) scales.

The sebaceous glands, lodged in the corium, are most abundant in parts exposed to friction. They generally open into the hair follicles, occasionally on the surface of the body. Each gland consists of a small duct which terminates in a lobulated recess. These lobules vary, and are, as is the duct, lined with epithelium. They are filled with sebaceous matter which, as it is secreted, is detached into the sacs. They are very plentiful between the claws of cattle.

The sudorific glands, or sweat glands, are situated in the subcutaneous areolar tissue, surrounded by a quantity of fat. They are small, round, reddish bodies, each of which consists of one or more fine tubes coiled into a ball, the free end of the tube being continued up through the true skin and cuticle, and opening on the surface. Each sweat gland is supplied with a cluster of capillary blood vessels which vary in size, being very large when perspiration is excessive. The contents of the smaller ones are fluid, and of the larger, semifluid.

The skin may be regarded as an organ supplementary in its action to the lungs and kidneys, since by its secretion it is capable of removing a considerable quantity of water from the blood; it also removes small quantities of carbon dioxid, salts, and in certain instances during suppression of the renal secretions a small quantity of urea. The skin is also the chief organ for the regulation of animal heat, by or through conduction, radiation, and evaporation of water, permitting of loss of heat, while it also, through other mechanisms, is able to regulate the heat lost. The hair furnishes protection against extreme and sudden variations of temperature by reason of the fact that hairs are poor conductors of heat, and inclose between them a still layer of air, itself a nonconductor. The hairs are also furnished with an apparatus by which the loss of heat may be regulated; thus, in cold weather, through the contraction of unstriped muscular fibers of the skin, the hairs become erect and the external coat becomes thicker. Cold, too, acts as a stimulus to the growth of hair, and we find, in consequence, a thicker coat in winter than in summer. The hairs also furnish protection against wet, as they are always more or less oily from the secretion of sebaceous glands, and thus shed water. Through their elasticity they furnish mechanical protection, and through the thickness of the coat, to a certain degree, resist the attacks of insects. Finally, the hairs assist the sense of touch.

The sweat glands are constantly discharging a watery secretion in the form of insensible perspiration, and by their influence act as regulators of the temperature of the body; hence, in warm weather, the secretion of the skin is increased, which tends to prevent overheating. Sweating, in addition to regulating heat, is also an active agent in removing effete material from the blood; therefore this secretion can not be checked without danger. If the skin is covered with an impermeable coating of grease or tar, death results from blood poisoning, owing to the retention of materials destined to be excreted by the skin.

All secretion poured out by the skin is not only modified by the condition of the atmosphere but also by the character and quantity of the food, by the amount of exercise, and especially by the quantity of fluid taken.

The sebaceous secretion is intended to lubricate the skin and hairs. It consists of soft, fatty material suspended in water, and is characterized by an odor peculiar to the animal by which it is secreted.

I will not attempt to classify the various diseases of the skin, for in a work of this kind it would serve only to confuse the reader.

We shall first consider a class of diseases which are of an inflammatory type; next, those caused by faulty secretion and abnormal growth; then, diseases of parasitic origin; lastly, local injuries of the skin.

PRURITIS (ITCHING).

We shall consider pruritis first as a distinct subject. It is not a disease, only a sensation, and therefore a symptom. It is one of the symptoms accompanying the majority of the diseases which we will consider in this chapter. It is, then, a functional affection produced by slight irritation from without or by an internal cause acting upon the sensory nerves of the skin. Nothing characteristic is seen except the secondary lesions, produced mechanically by scratching or rubbing.

There are various forms of itching, the result of specific skin diseases, where the pruritis is a secondary symptom. In such cases it should not be regarded as an independent affection.

Causes.—Many causes may induce the condition which we recognize here as pruritis. The most common one is dirt on the skin, resulting from insufficient care. If the ceiling of the stable is open, so that dust and straw may fall, the skin is irritated and pruritis results. It also occurs in some forms of indigestion.

The parts of the body most exposed to this condition are the croup, the back, the top of the neck, and the root of the tail.

Another cause is found in affections of the liver and of the kidneys, when an increase of effete material has to be thrown off by the skin. Morbid materials circulating in the blood may produce a tickling or smarting sensation of the skin in their passage from the blood to the free surface of the skin. Certain irritating substances when eaten may be excreted by the skin, and coming thus in direct contact with the sensory nerves produce itching, or may go further and cause distinct inflammation of the skin. In another class of cases the pruritis may be ascribable to an atrophy, contraction, or hardening of the skin, when the nerves become irritated by the pressure. These conditions may be so slightly marked in a thick skin like that of the ox that they can not be recognized. It is frequently noticed that cattle rub themselves as soon as they pass from the stable into the open air—changing from a warm to a cold atmosphere. Again, we may find one that does all its rubbing in the stall. We may look for lice, but fail to find them. These conditions are generally attributable to high feeding and to too close confinement. They may be associated with inflammatory irritation or not; certainly we fail to discover any morbid changes in the skin. There is to some extent a delightful sensation produced by rubbing, and it may partly become a habit of pleasure.

Treatment.—We must place our chief reliance upon a change of food, plenty of exercise, and in most cases the administration of an active cathartic—1 to 1½ pounds of Epsom salt, a handful of common salt, a tablespoonful of ginger or pepper, mixed with 2 quarts of water, all of which is to be given at one dose. Afterwards half an ounce of hyposulphite of soda mixed with the feed may be given twice a day for a week. For an external application, when the skin is abraded or thickened from rubbing, a solution of borax, 4 ounces to the quart of water, may be used. Carbolic acid, ½ ounce to a quart of water, will give relief in some cases.

INFLAMMATORY DISEASES OF THE SKIN.

ERYTHEMA.

This is the simplest form of inflammation of the skin. It consists of an increased redness, which may occur in patches or involve considerable surface. The red coloration disappears when pressed by the finger, but soon returns after the pressure is removed. There is seldom much swelling of the affected part, though often there is a glutinous discharge which dries and mats the hair or forms a thin scale upon the skin. In simple erythema the epidermis alone is affected; when it becomes chronic, fissures form and extend into the corium, or true skin.

Causes.—Simple erythema, consisting of an inflammatory irritation, is seen in very young calves, in which the navels leak. The discharge being urine, it causes an irritation of the surrounding skin. Chafing, which is another form of erythema, is occasionally seen on the udders of cows from rubbing by the legs; chafing between the legs is not uncommon among fat steers. Chronic erythema is found in the form of chapped teats of cows and chapped lips in sucking calves. It frequently occurs in cows when they are turned out in winter directly after milking, and in others from chafing by the sucking calf. Some cows are peculiarly subject to sore teats. The fissures when neglected in the early stage of formation become deep, very painful, often bleeding at the slightest touch, and when milked in that condition cause the animal to become a kicker. Occasionally the lower portions of the legs become irritated and chapped when cattle are fed in a muddy or wet yard in winter, or if they are compelled to wade through water in frosty weather. Another form of erythema occurs in young cattle highly fed and closely stabled for a long winter. The erythema appears in patches, and as it is most common near the end of the winter it is known as the "spring eruption" or "spring itch."

Treatment.—In ordinary cases of erythema the removal of the cause and the application of benzoated oxid of zinc ointment, carbolized cosmoline, or ichthyol ointment applied a few times, will restore the skin to a healthy condition.

When there are fissures the zinc ointment is the best. If at the teats, a milk siphon (Pl. XXIV, fig. 4) should be used instead of milking by hand, and the calf, if one is suckled, should be taken away. The calf should be fed by hand if its mouth is affected. When the legs are irritated or chapped, dry stabling for a few days and the application of tar ointment will soon heal them.

URTICARIA (NETTLE RASH, OR SURFEIT).

This is a mild, inflammatory affection of the skin, characterized by sudden development of patches of various sizes, from that of a nickel to one as large as the hand. The patches of raised skin are marked by an abrupt border and are irregular in form. All the swelling may disappear in a few hours, or it may go away in one place and reappear on another part of the body. It is always accompanied with a great desire to rub the affected part. In its simplest type, as just described, it is never followed by any serous exudation or eruptions, unless the surface of the skin becomes abraded from scratching or rubbing.

Causes.—Digestive derangements caused by overloading the stomach when the animal is turned out to graze in the spring, certain feed constituents, high feeding of fattening stock, functional derangement of the kidneys, spinal and other nervous affections, are the most common sources of nettle rash.

The disease consists in paralysis of the nerve ends that control the volume of the capillary vessels in certain areas of skin, thus permitting the vessels to expand, their contents in part to exude, and thus produce a soft, circumscribed swelling.

Treatment.—Administer a full dose of Epsom salt. Give soft, easily digested feed, and wash the affected parts with a solution of bicarbonate of soda (common baking soda), 8 ounces to the gallon of water twice a day, or diluted glycerin may be applied to the skin. If it assumes a persistent tendency, give a tablespoonful of the following powder in the feed three times a day: Cream of tartar, sulphur, and nitrate of potassium, equal parts by weight; mix.

ECZEMA.

Eczema is a noncontagious inflammation of the skin, characterized by any or all of the results of inflammation at once or in succession, such as erythema, vesicles, or pustules, accompanied with more or less infiltration and itching, terminating in a watery discharge, with the formation of crusts or in scaling off. The disease may run an acute course and then disappear, or it may become chronic; therefore two varieties are recognized, vesicular (or pustular) and chronic eczema.

Causes.—Eczema is not so common among cattle as in horses and in dogs, in which it is the most common of all skin diseases. Among cattle it is occasionally observed under systems of bad hygiene, filthiness, lousiness, overcrowding, overfeeding, excessively damp or too warm stables. It is found to develop now and then in cattle that are fed upon sour substances, distillery swill, house or garden garbage, etc. Localized eczema may be caused by irritant substances applied to the skin—turpentine, ammonia, the essential oils, mustard, Spanish-fly ointment, etc. Occasionally an eruption with vesiculation of the skin has been induced by the excessive use of mercurial preparations for the destruction of lice. It is evident that eczema may arise from local irritation to the skin or from an autointoxication. Cattle fed on the refuse from potato-starch factories develop a most obstinate and widespread eczema, beginning on the legs.

Symptoms.—In accordance with the variety of symptoms during the progress of the disease we may divide it into different stages or periods: (1) Swelling and increased heat of the skin; the formation of vesicles, which are circumscribed, rounded elevations of the epidermis, varying in size from a pinhead to a split pea, containing a clear, watery fluid; (2) exudation of a watery, glutinous fluid, formation of crusts, and sometimes suppuration, or the formation of vesicles containing pus (pustules); (3) scaling off (desquamation), with redness, and thickening of the skin. From the very beginning of the disease the animal commences to rub the affected parts; hence the various stages may not always be easily recognized, as the rubbing produces more or less abrasion, thus leaving the skin raw— sometimes bleeding. Neither do these symptoms always occur in regular succession, for in some cases the exudation is most prominent, being very profuse, and serve to spread the disorder over a large surface. In other cases the formation of incrustations, or rawness of the skin, is the most striking feature. The disease may be limited to certain small areas, or it may be diffused over the greater part of the body; the vesicles, or pustules, may be scattered in small clusters, or a large number run together. The chronic form is really only a prolongation of the disease, successive crops of pustules appearing on various portions of the body, frequently invading fresh sections of the skin, while the older surfaces form scabs, or crusts, upon the raw, indurated skin.

In old, standing cases the skin breaks, forming fissures, especially on portions of the body that bend—the neck and limbs. Thus the disease may be prolonged indefinitely. When eczema reaches its latest period, either acute or chronic, desquamation of the affected parts is the most prominent feature. The formation and shedding of these successive crops of scales constitute the character of the disease frequently denominated psoriasis.

Treatment.—The treatment of eczema is often anything but a pleasant task. There is no one method of treatment which always proves successful, no matter how early it is begun or how small an area is involved. We must endeavor to remove the cause by giving attention to the general health of the animal and to its environment. Feeding should be moderate in quantity and not too stimulating in character—green feed, bran mashes, ground oats, clean hay, plenty of salt. If the animal has been fed too high, give an active purgative—Epsom salt preferred—once a week, if necessary, and half an ounce of acetate or nitrate of potassium may be given in the feed twice a day. If the animal is in poor condition and debilitated, give a tablespoonful of the following mixture in feed twice a day: Powdered copperas, gentian, sulphur, and sassafras bark, equal parts by weight. If the animal is lousy, the parasite must be destroyed before the eczema can be cured. The external treatment must vary with the character of the lesions; no irritating application is to be made while the disease is in its acute vesicular, or pustular, stage, and, in the chronic stage, active stimulants must be used. Much washing is harmful, yet crusts and scales must be removed in order to obtain satisfactory results from the external applications. Both objects, however, can be attained by judiciously combining the curative agents with such substances as will at the same time cleanse the parts.

In the vesicular stage, when the skin is feverish and the epidermis peeling off, thus exposing the exuding dermis, an application of boric-acid solution, 2 drams of the acid to 8 ounces of water, often relieves the smarting or itching, and also serves to check the exudation and dry the surface. If this fails to have the desired effect compound cresol, 1 ounce to 2 quarts of water, should be used as a wash. Either of these washes may be used several times a day until incrustation is well established. Then compound cresol, 1 ounce to 2 quarts of sweet oil, or the benzoated oxid of zinc ointment, giving the affected surfaces a thorough application once a day, will be efficacious. When the eczema is not the result of an external irritant, it takes usually from one to two weeks to heal.

In chronic eczema, when there is a succession of scabs or scales, indolent sores or fissures, the white precipitate ointment, nitrate of mercury ointment, or blue ointment, mixed with equal parts of cosmoline or fresh lard, may be applied every second day, taking care to protect the parts so that the animal can not lick it off.

The internal administration of arsenic often yields excellent results in chronic eczema. Dissolve 1 dram of arsenic and 1 dram of carbonate of potassium in 1 pint of boiling water, and give 1 ounce of this twice a day in water, after feeding. An alkali internally may be of service. As such, one may give 2 ounces of bicarbonate of soda twice daily. Sublimed sulphur may also be tried in ounce doses twice daily.

PUSTULES (IMPETIGO).

Impetigo is an inflammatory disease of the skin, characterized by the formation of distinct pustules, about the size of a pea or a bean, without itching. The pustules develop from the papular layer of the skin, and contain a yellowish-white pus. After reaching maturity they remain stationary for a few days, then they disappear by absorption and dry up into crusts, which later drop off, leaving upon the skin a red spot that soon disappears. Occasionally the crusts remain firmly adherent for a long time, or they may be raised and loosened by the formation of matter underneath. The dry crusts usually have a brown or black appearance.

Causes.—Impetigo affects sucking calves, in which the disease appears upon the lips, nostrils, and face. It is attributed to some irritant substance contained in the mother's milk. Impetigo is also witnessed among grazing animals, regardless of age, and it especially attacks animals with white hair and skin. The mouth, face, and limbs become covered with pustules, which may rupture in a few hours, followed by rapid and successive incrustations; the scabs frequently coalesce, covering a large surface; pus may form under them, and thus the whole thickness of the skin become involved in the morbid process. This form of the disease is attributed to the local irritant properties of such plants in the pasture as St. John's wort (Hypericum perforatum), smartweed (Polygonum hydropiper), vetches, honeydew, etc. Buckwheat, at the time the seeds become ripe, is said to have caused it; also bedding with buckwheat straw.

Treatment.—Sucking calves should be removed from the mother, and a purgative given to the latter to divert the poisonous substance secreted with the milk. When the more formidable disease among grazing cattle appears, the pasturage should be changed and the affected parts of the animal thoroughly anointed once a day with sweet oil containing 2 drams of carbolic acid to the pint. This should be continued until the crusts soften and begin to drop off, then the parts may be cleansed thoroughly with warm water and soap. Subsequently the white precipitate ointment or carbolized cosmoline should be applied daily until the parts are healed.

PEMPHIGUS (WATER BLISTERS).

This is an inflammatory disease of the skin, characterized by successive formations of rounded, irregularly shaped water blisters, varying in size from a pea to a hen's egg.

Causes.—Obscure.

Symptoms.—The formation of a blister is preceded by a congestion or swelling of the skin. Yellowish-colored water collects beneath the cuticle, which raises the latter from its bed in the form of a blister. The blisters appear in a succession of crops; as soon as one crop disappears another forms. They usually occur in clusters, each one being distinct, or they may coalesce. Each crop usually runs its course in a week. The disease is attended with itching or burning sensations which cause the animal to rub, thereby frequently producing excoriations and formation of crust on the affected region.

Treatment.—Give a tablespoonful of the following-described mixture in feed twice a day: Saltpeter, cream of tartar, and sulphur, equal parts by weight. The blisters should be opened as soon as formed, to allow the escape of the serum, followed by a wash composed of chlorid of zinc, 1 dram to 15 ounces of water. When there is any formation of crusts, carbolized cosmoline should be applied.

FURUNCULUS (BOILS).

This is an acute affection of the skin, usually involving its whole thickness, characterized by the formation of one or more abscesses, originating generally in a sebaceous gland, sweat gland, or hair follicle. They usually terminate by absorption, or by the formation of a central core, which sloughs out, leaving a deep, round cavity that soon heals.

Causes.—Impoverished state of blood, the result of kidney diseases or of local friction or contusions, with the entrance of pus cocci through the damaged skin or through a hair follicle or a sebaceous gland.

Symptoms.—Boils in cattle usually appear singly, not in clusters; they may attain the size of a hen's egg. The abscess begins as a small round nodule, painful on pressure, gradually increases in size until death of the central portion takes place, then the surface of the skin gives way to internal pressure and the core is released and expelled. Constitutional symptoms are generally absent, unless the boils occur in considerable numbers, or by their size involve a great deal of tissue.

Treatment.—Poulticing to ripen the abscess. If this can not be done, apply camphorated oil two or three times a day until the core is formed. As soon as the central or most prominent part becomes soft, the abscess should be opened to release the core. Then use carbolized cosmoline once a day until the healing is completed. If the animal is in poor condition, give tonics—copperas, gentian, ginger, and sulphur, equal parts by weight, 1 tablespoonful twice a day. If the animal manifests a feverish condition of the system, give half an ounce of saltpeter twice a day, continuing it several days or a week.

FAULTY SECRETIONS AND ABNORMAL GROWTHS OF THE SKIN.

PITYRIASIS (SEBORRHEA, DANDRUFF, OR SCURF).

This is a condition characterized by an excessive secretion of sebaceous matter, forming upon the skin in small crusts or scales.

Causes.—It is ascribable to a functional derangement of the sebaceous glands, usually accompanied with dryness and loss of pliancy of the skin. The animal is hidebound, as it is commonly termed, thin in flesh, inclined to rub, and very frequently lousy. The condition is observed most often toward the spring of the year. Animals that are continually housed, and the skins of which receive no cleaning, generally present a coat filled with fine scales, composed of epithelium from the epidermis and dried sebaceous matter. This, however, is a physiological condition and compatible with perfect health.

Symptoms.—Pityriasis may affect the greater portion of the body, though usually only certain parts are affected—the ears, neck, rump, etc. The skin becomes scurfy, the hairy coat filled with branlike gray or whitish scales.

Treatment.—Nutritious feed, such as oil-cake meal, bran, ground oats, and clean hay. In the spring the disease generally disappears after the animal is turned out to pasture. When lice are present they should be destroyed.

ELEPHANTIASIS (SCLERODERMA).

This condition consists in a chronic thickening of the skin, which may affect one or more limbs or involve the whole integument. It is characterized by recurrent attacks of swelling of the skin and subcutaneous areolar tissue. After each attack the affected parts remain infiltrated to a larger extent than before, until finally the skin may attain a thickness of an inch, becoming wrinkled and fissured. In cattle this disease is confined to hot climates. The predisposing cause is unknown.

EDEMA (ANASARCA OF THE SKIN).

This is a dropsical condition of the skin and subcutaneous areolar tissue, characterized by pitting under pressure, the fingers leaving a dent which remains a short time.

Causes.—Edema generally results from a weakened state of the system arising from previous disease. It may also be dependent upon a functional derangement of the kidneys, upon weak circulation, or obstruction to the flow of blood through the lungs. In debilitated animals and in some animals highly infested with parasites there is swelling of the dewlap or of the fold of the skin between the jaws.

Symptoms.—Painless swelling of a limb, udder, lower surface of abdomen, or lower jaw becomes apparent. This may increase in dimensions for several days or may attain its maximum in less than 24 hours. Unless complicated with some acute disease of a specific character, there is not much, if any, constitutional disturbance. The deep layer of the skin is infiltrated with serum, which gives it the characteristic condition of pitting under pressure.

Treatment.—When the cause can be ascertained and removed we may expect to see the edema disappear. When no direct specific cause can be discovered and the animal is debilitated, give general tonic. If, on the contrary, it is in good flesh, give a purgative, followed by half an ounce of acetate of potassium twice a day. External applications are useless.

Edema may be distinguished from erysipelas or anthrax by the absence of pain and fever.

DERMOID AND SEBACEOUS CYSTS (WENS).

A dermoid cyst is formed by an involution of the skin with a growth of hair on the inner wall of the sac. It may become embedded deeply in the subcutaneous tissues or may just penetrate the thickness of the skin, where it is movable and painless. They are generally found within the ear or at its base, although they may form on any part of the body. Usually they have a small opening, from which a thick, cheesy matter can be squeezed out. The rational treatment is to dissect them out.

Sebaceous cysts appear not unlike the former. They are formed by a dilatation of the hair follicle and sebaceous duct within the skin, and contain a gray or yellowish sebaceous mass. The tumor may attain the size of a cherry stone or a walnut. Generally they are round, movable, and painless, soft or doughy in consistency, and covered with skin and hair. They develop slowly. The best treatment is to dissect out the sac with contents entire.

VERRUCA (WARTS).

Cattle are affected with two varieties of warts. One, the verruca vulgaris, is composed of a cluster of enlarged papillæ, covered with a thickened epidermis, the number of papillæ determining the breadth and their length its height. They are generally circular in figure, slightly roughened on the surface, and spring from the skin by a broad base. Occasionally large numbers of very thin, long, pedunculated warts grow from the skin of the ear, lips, about the eyes, and vulva. Another variety, the verruca acuminata, sometimes erroneously denominated epithelial cancers, are irregularly shaped elevations, tufted or club shaped, occasionally existing as thick, short, fleshy excrescences, giving the growth the appearance of granulation tissue. Their color is red or purplish, and oftentimes by friction they become raw and bleeding, emitting then a very offensive odor. They usually grow in clusters and their development is rapid.

Causes.—An abnormal nutrition of the skin, determined by increased energy of growth operating upon a healthy skin; at other times, upon a weak or impoverished skin.

Treatment.—When they are small and pedunculated, they may be snipped off with shears and the stump touched with nitrate of silver. When they are broad and flattened, they may be dissected out and the wound cauterized if necessary. If they are large and very vascular, they may be ligated, one by one, by taking a strong cord and tying it as firmly around the base as possible. They will then shrivel, die, and drop off. If there is a tendency to grow again, apply a red-hot iron or nitric acid with a glass rod. Very often warts quickly disappear if they are kept soft by daily applications of sweet or olive oil.

KELIS.

Kelis is an irregularly shaped flat tumor of the skin, resulting from hypertrophy—increased growth of the fibrous tissue of the corium, producing absorption of the papillary layer.

Causes.—It may arise spontaneously or follow a scar after an injury.

Symptoms.—Kelis generally appears below the knee or hock, and may occur singly or in numbers. There are no constitutional symptoms. Its growth is very slow and seldom causes any inconvenience. It appears as a flattened, irregular, or spreading growth within the substance of the skin, is hard to the touch, and is especially characterized by divergent branches or roots, resembling the claws of a crab; hence the name. Occasionally some part of it may soften and result in an abscess. It may grow several inches in length and encircle the whole limb.

Treatment.—So long as it causes the animal no inconvenience it is best not to meddle with it; when it does the animal ought to be fattened for beef, the meat being perfectly harmless to the consumer.

PARASITIC DISEASES OF THE SKIN.

RINGWORM (TINEA TONSURANS AND TINEA FAVOSA).

Ringworm is an affection of the skin, caused by a vegetable parasite.

The form known as tinea tonsurans is produced by the presence of a minute or microscopic fungus—the Trichophyton tonsurans, which affects the hair and the epidermic layer of the skin, and is highly contagious, being readily transmitted from one animal to another. This fungus consists of spores and filaments. The spores, being the most numerous, are round and seldom vary much in size. They are very abundant in the hair follicle. The filaments are articulated, waving, and contain granules. This disease is productive of changes in the root and shaft of the hair, rendering it brittle and easily broken off.

This disease becomes manifest by the formation of circular patches on the skin, which soon becomes denuded of hair. The cuticular layer of the skin in slightly inflamed, and vesication with exudation occurs, followed by the formation of scaly, brittle crusts. The patches appear silvery gray when incrusted, and are mostly confined to the head and neck. It is a common disease among young cattle in the winter and spring. Very early in the development of the patches the hairs split, twist, and break off close to the skin. This disease is attended with more or less itching. It is communicable to man.

Tinea favosa comes from another fungus, the Achorion schönleinii. This enters the hair follicle and involves the cuticle surrounding it, small crusts form which increase in diameter and thickness and then become elevated at their margin, forming a cup-shaped scab, the favus cup, which gives the disease its distinctive character. The number of these cups varies from a few to many hundreds. The hairs involved become brittle and broken, fall off with the crusts, leaving small bald patches. The crusts are of a pale or sulphur-yellow color at first; as they grow older they turn darker, or to a brown color. This form of ringworm has a peculiar odor, resembling that of mice or musty straw. It is occasionally communicated to cattle by man, mice, cats, etc., all being subject to it.

Treatment.—Remove all crusts by washing with soap and water, then apply acetic acid, sulphur ointment, tincture of iodin or nitrate of mercury ointment once a day. Cleanse the stable and whitewash it to destroy the spores scattered by the crusts.

OTHER PARASITES AND PARASITIC DISEASES OF THE SKIN.

For discussion of mange, itch, scab, lousiness, warbles (grub in the skin), buffalo gnats, hornfly (Hæmatobia serrata), ticks, flies, etc., see the chapter on "The animal parasites of cattle," page 502.

WOUNDS OF THE SKIN.

SNAKE BITES AND VENOMOUS STINGS.

[See discussion of these subjects in chapter on "Poisons and poisoning."]

BURNS AND SCALDS.

This is a rare accident among cattle, yet in cases of fire it may occur. The application of heat, whether dry or moist, unless sufficient instantly to destroy the life of a part, is always followed by the development of vesicles or blisters, which contain a thin, watery fluid. The blisters may be isolated and not very large, or one blister may cover a very large surface. When the burn is very severe the skin may be wholly devitalized, or the injury may extend into the deeper structures of the skin. Then sloughs will occur, followed by a contraction of the parts in healing; if on a limb, this may render the animal stiff. When the burn or scald has been a severe one, the resulting pain is great and the constitutional disturbance very marked.

Treatment.—For a superficial burn use a mixture of equal parts of limewater and linseed oil, or common white paint—white lead ground in oil—to exclude the atmosphere and protect the inflamed skin. If it is not convenient to get anything else, chimney soot, flour, or starch may be spread on the wound (dry), and covered with cotton batting and light bandage. The blisters should be opened to let the contained fluid escape, but do not pull off the thin cuticle which has been raised by the blister. When the burn is extensive and deep sloughing occurs, the parts should be treated, like other deep wounds, by poulticing, astringent washes, etc. When the system has sustained much shock, the animal may require internal stimulants, such as 2 drams of carbonate of ammonia every hour until it rallies. When the pain is very great, hypodermic injections of 6 grains of morphia may be administered every six hours.

Frostbite on any portion of the body may be treated as recommended in the article on diseases of the ears.

EMPHYSEMA (AIR OR GAS UNDER THE SKIN).

Emphysema of the skin is not a true disease of the skin, but it is mentioned as a pathological condition. It is characterized by a distention of the skin with air or gas contained in the subcutaneous areolar tissue. It may depend upon a septic condition of the blood, as in anthrax or blackleg, or air may be forced under the skin about the head, neck, and shoulders, as a result of rupture of the windpipe. It occurs in the region of the chest and shoulders from penetrating wounds of the chest and lung, and occasionally follows puncture of the rumen when the escaping gas is retained under the skin.

Symptoms—The skin is enormously distended over a greater or less portion of the body; thus any region of the body may lose its natural contour and appear like a monstrosity. There is a peculiar crackling beneath the skin when the hand is passed over it, and on tapping it with the fingers a resonant, drumlike sound is elicited.

Treatment.—Puncture the distended skin with a clean, broad-bladed knife and press the air out. Further treatment must be directed with a view to the removal of the cause.