Part 85

Aconite may be given in conjunction with the niter when the heart is greatly excited and beats strongly. Ten-drop doses, repeated every 2 hours for 24 hours, are sufficient. The use of cathartics is dangerous, for they may excite superpurgation. Usually the niter will relieve the constipation; yet if it should prove obstinate, laxatives may be carefully given. Bleeding, both general and local, should be guarded against. The shoes must be early removed and the soles left unpared.

Paring of the soles presents two objections: First, while it may temporarily relieve the pain by relieving pressure, it favors greater exudation, which may more than counterbalance the good effects. Secondly, it makes the feet tender and subject to bruises when the animal again goes to work. The shoes should be replaced when convalescence sets in and the animal is ready to take exercise. Exercise should never be enforced until the inflammation has subsided; for although it temporarily relieves the pain and soreness it maintains the irritation, increases the exudation, and postpones recovery.

If at the end of the fifth or sixth day prominent symptoms of recovery are not apparent, apply a stiff blister of cantharides around the coronet and omit the niter for about 48 hours. When the blister is well set, the feet may again receive wet swabs. If one blister does not remove the soreness it may be repeated, or the actual cautery applied. The same treatment should be adopted where sidebones form or inflammation of the coronet bone follows. When the sole breaks through, exposing the soft tissues, the feet must be carefully shod with thin heels and thick toes if there is a tendency to walk on the heels, and the sole must be well protected with appropriate dressings and pressure over the exposed parts. When there is turning up of the toe, blistering of the coronet, in front only, sometimes stimulates the growth of horn, but as a rule judicious shoeing is the only treatment that will enable the animal to do light, slow work.

When suppuration of the laminae is profuse, it is better to destroy your patient at once and relieve his suffering: but if the suppuration is limited to a small extent of tissue, especially of the sole, treatment, as in acute cases, may induce recovery and should always be tried. If from bed sores or other causes septicemia or pyemia is feared, the bisulphite of soda, in half-ounce doses, may be given in conjunction with tonics and such other treatment as is indicated in these diseases.

As to enforced recumbency I doubt the propriety of insisting on it in the majority of cases, for I think the patient usually assumes whatever position gives most comfort. No doubt recumbency diminishes the amount of blood sent to the feet, and may greatly relieve the pain, so that forcing the patient to lie down may be tried, yet should not be renewed if he thereafter persists in standing.

When the animal persistently stands, or constant lying indicates it (to prevent extensive sores), the patient should be placed in slings. When all four feet are affected it may be impossible to use slings, for the reason that the patient refuses to support any of his weight and simply hangs in them. Lastly, convalescent cases must not be returned to work too early, else permanent recovery may never be effected.

DISEASES OF THE SKIN.

By JAMES LAW, F. R. C. V. S.,

Formerly Professor of Veterinary Science, etc., Cornell University.

As we find them described in systematic works, the diseases of the skin are very numerous and complex, which may be largely accounted for by the fact that the cutaneous covering is exposed to view at all points, so that shades of difference in inflammatory and other diseased processes are easily seen and distinguished from one another. In the horse the hairy covering serves to some extent to mask the symptoms, and hence the nonprofessional man is tempted to apply the term "mange" to all alike, and it is only a step further to apply the same treatment to all these widely different disorders. Yet even in the hairy quadruped the distinction can be made in a way which can not be done in disorders of that counterpart and prolongation of the skin--the mucous membrane, which lines the air passages, the digestive organs, the urinary and generative apparatus. Diseased processes, therefore, which in these organs it might be difficult or impossible to distinguish from one another, can usually be separated and recognized when appearing in the skin.

Nor is this differentiation unimportant. The cutaneous covering presents such an extensive surface for the secretion of cuticular scales, hairs, horn, sebaceous matter, sweat, and other excretory matters, that any extensive disorder in its functions may lead to serious internal disease and death. Again, the intimate nervous sympathy of different points of the skin with particular internal organs renders certain skin disorders causative of internal disease and certain internal diseases causative of affections of the skin. The mere painting of the skin with an impermeable coating of glue is speedily fatal; a cold draft striking on the chest causes inflammation of the lungs or pleura; a skin eruption speedily follows certain disorders of the stomach, the liver, the kidneys, or even the lungs; simple burns of the skin cause inflammations of internal organs, and inflammation of such organs cause in their turn eruptions on the skin. The relations--nervous, secretory, and absorptive--between the skin and internal organs are most extensive and varied, and therefore a visible disorder in the skin may point at once and specifically to a particular fault in diet, to an injudicious use of cold water when the system is heated, to a fault in drainage, ventilation, or lighting of the stables, to indigestion, to liver disease, to urinary disorder, etc.

THE SKIN AND ITS DISEASES.]

STRUCTURE OF THE SKIN.

The skin consists primarily of two parts: (1) The superficial nonvascular (without blood vessels) layer, the cuticle, or epidermis; and (2) the deep vascular (with blood vessels) layer, the corium, dermis, or true skin. (See Pl. XXXVIII, fig. 1.)

The cuticle is made up of cells placed side by side and more or less modified in shape by their mutual compression and by surface evaporation and drying. The superficial stratum consists of the cells dried in the form of scales, which fall off continually and form dandruff. The deep stratum (the mucous layer) is formed of somewhat rounded cells with large central nuclei, and in colored skin containing numerous pigment granules. These cells have prolongations, or branches, by which they communicate with one another and with the superficial layer of cells in the true skin beneath. Through these prolongations they receive nutrient liquids for their growth and increase, and pass on liquids absorbed by the skin into the vessels of the true skin beneath. The living matter in the cells exercises an equally selective power on what they shall take up for their own nourishment and on what they shall admit into the circulation from without. Thus, certain agents, like iodin and belladonna, are readily admitted, whereas others, like arsenic, are excluded by the sound, unbroken epidermis. Between the deep and superficial layers of the epidermis there is a thin, translucent layer (septum lucidum) consisting of a double stratum of cells, and forming a medium of transition from the deep spheroidal to the superficial scaly cuticle.

The true skin, or dermis, has a framework of interlacing bundles of white and yellow fibers, large and coarse in the deeper layers, and fine in the superficial, where they approach the cuticle. Between the fibrous bundles are left interspaces which, like the bundles, become finer as they approach the surface, and inclose cells, vessels, nerves, glands, gland ducts, hairs, and in the deeper layers fat.

The superficial layer of the dermis is formed into a series of minute, conical elevations, or papillae, projecting into the deep portion of the cuticle, from which they are separated by a very fine transparent membrane. This papillary layer is very richly supplied with capillary blood vessels and nerves, and is at once the seat of acute sensation and the point from which the nutrient liquid is supplied to the cells of the cuticle above. It is also at this point that the active changes of inflammation are especially concentrated; it is the immediately superposed cell layers (mucous) that become morbidly increased in the earlier stages of inflammation; it is on the surface of the papillary layer that the liquid is thrown out which raises the cuticle in the form of a blister, and it is at this point mainly that pus forms in the ordinary pustule.

The fibrous bundles of the true skin contain plain, muscular fibers, which are not controlled by the will, but contract under the influence of cold and under certain nervous influences, as in some skin diseases and in the chill of a fever, and lead to contraction, tightening, or corrugation of the skin, contributing to produce the "hidebound" of the horseman. Other minute, muscular filaments are extended from the surface of the dermis to the hair follicle on the side to which the hair is inclined, and under the same stimulating influences produce that erection of the hair which is familiarly known as "staring coat." Besides these, the horse's skin is furnished with an expansion of red, voluntary muscle, firmly attached to the fibrous bundles, and by which the animal can not only dislodge insects and other irritants, but even shake off the harness. This fleshy envelope covers the sides of the trunk and the lower portions of the neck and head, the parts unprotected by the mane and tail, and serves to throw the skin of these parts into puckers, or ridges, in certain irritating skin diseases.

The hairs are cuticular products growing from an enlarged papilla lodged in the depth of a follicle or sac, hollowed out in the skin and extending to its deepest layers. The hair follicle is lined by cells of epidermis, which at the bottom are reflected on the papilla and become the root of the hair. The hair itself is formed of the same kind of cells firmly adherent to one another by a tough, intercellular substance, and overlapping each other, like slates on a roof, in a direction toward the free end.

The sebaceous glands are branching tubes ending in follicles or sacs and opening into the hair follicles, lined by a very vascular fibrous network representing the dermis, and an internal layer of cells representing the mucous layer of the cuticle. The oily secretion gives gloss to the hair and prevents its becoming dry and brittle, and keeps the skin soft and supple, protecting it at once against undue exhalation of water and undue absorption when immersed in that medium. Besides those connected with the hair follicles there are numerous, isolated, sebaceous glands, opening directly on the surface of the skin, producing a somewhat thicker and more odorous secretion. They are found in large numbers in the folds of the skin, where chafing would be liable if the surface were dry, as on the sheath, scrotum, mammary glands, and inner side of the thigh, around the anus and vulva, in the hollow of the heel, beneath the fine horn of the frog, on the inner side of the elbow, on the lips, nostrils, and eyelids. When closed by dried secretion or otherwise these glands may become distended so as to form various-sized swellings on the skin, and when inflamed they may throw out offensive, liquid discharges, as in "grease," or produce red, tender fungous growths ("grapes.")

The sweat glands of the horse, like those of man, are composed of simple tubes, which extend down through the cuticle and dermis in a spiral manner, and are coiled into balls in the deeper layer of the true skin. In addition to their importance in throwing offensive waste products out of the system, these glands tend to cool the skin and the entire economy of the animal through the evaporation of their watery secretion. Their activity is therefore a matter of no small moment, as besides regulating the animal heat and excreting impurities, they influence largely the internal organs through the intimate sympathy maintained between them and the skin.

Diseases of the skin may be conveniently divided, according to their most marked features, into--

(1) Those in which congestion and inflammation are the most marked features, varying according to the grade or form into (a) congestion with simple redness, dryness, and heat, but no eruption (erythema); (b) inflammation with red-pointed elevations, but no blisters (papules); (c) inflammation with fine, conical elevations, each surmounted by a minute blister (vesicle); (d) inflammation with a similar eruption but with larger blisters, like half a pea and upwards (bullae); (e) inflammation with a similar eruption, but with a small sac of white, creamy pus on the summit of each elevation (pustules); (f) the formation of pustules implicating the superficial layer of the true skin, a small portion of which dies and is thrown off as a slough, or "core" (boils); (g) the formation of round, nodular, transient swellings in the true skin (tubercles); and (h) the excessive production of scales, or dandruff (scaly or squamous affections).

(2) Diseases in which there are only deranged sensations of itching, heat, tenderness, etc. (neurosis).

(3) Diseased growths, such as warts, callosities, horny growths, cancer, etc.

(4) Diseases from parasites, animal and vegetable.

(5) Diseases connected with a specific poison, such as horsepox, erysipelas, anthrax, farcy, or cutaneous glanders, etc.

(6) Physical injuries, like wounds, burns, scalds, etc.