DISEASES OF THE SKIN.
Ultimate skin lesions in man and animals similar. Masked by thick cuticle, pigment, hair, fur, feathers. White, hairless skin. Lesions and deranged functions: Maculæ, erythema, papules, nodules, blisters, blebs, pustules, boils, carbuncles, scales, crusts, sitfasts, horny growths, erosions, abrasions, chaps, fissures, ulcers, excrescences, cicatrices, neuroses, morbid secretions, changes in glands, hairs, in derma. Scleroderma. Elephantiasis. Vegetable and animal parasites.
In cutaneous diseases in man and animals the actual lesions are largely of the same nature, yet in the animal covered with hair, fur or feathers, and with the cuticle deeply pigmented, the diagnosis of the different affections becomes much more difficult. On white-skinned animals and on parts with little or no hair, the identification of the different forms is usually possible. The following list may serve to indicate the nature of the different lesions, but these must not be accepted as indicating distinct diseases, as two or more of these forms often coexist or succeed each other in the same affection:—
1st. Maculæ: Spots: Discolorations. Examples: Black, melanotic spots in skins of white horses: white spots in dourine, after pustules, etc.: ecchymosis after contusions, stings, insect bites, etc.: petechial spots in anthrax, rouget, hog cholera, rinderpest, canine distemper, swine plague, scurvy, etc.
2d. Erythema: Rash: Flush. Congestive redness usually disappearing under pressure. Physiological in blush or glow of exercise, pathological from insolation, friction, deranged innervation, etc.
3d. Papulæ: Papules: Pimples. Small, red, hard, conical elevations, not forming blister nor pustule. Due to exudation and the accumulation of leucocytes at given points, having a local or general cause, (psoriasis, intertrigo, etc.).
4th. Tuberculæ: Nodules. Larger but still circumscribed thickening of the entire skin from exudation and cell growth, from ½ inch to 2 or more inches in diameter and sometimes becoming confluent. Examples: Urticaria (surfeit) in solipeds, and cattle; petechial fever, farcy, etc. Sometimes chronic.
5th. Vesiculæ: Blisters. Rounded or conical elevations the size of a millet seed to a pea, and having a small liquid exudation under the cuticle in the centre. In inflammations of the papillary layer, of a sufficiently acute type the tendency is to the formation of vesicles. These lesions are, therefore, often present in very different forms of skin disease from those due to simple thermic irritation, to constitutional diseases like eczema, or contagious ones like sheep pox. May merge into pustules or other advanced lesions.
6th. Phlyctenæ: Bullæ: Blebs. In these the individual lesion is larger than in vesicles. They are of any size from a pea upward. The most striking example is in cantharides, blisters, scalds and burns, but in other cases it depends on a constitutional condition or a specially exudative dermatitis.
7th. Pustulæ: Pustules. These differ from vesicles in that the central exudate becomes the seat of suppuration and a limited collection of pus, at first central, though later involving, it may be the whole area of the exudate. It is often merely an advanced stage of the papule or vesicle. We find examples in the different forms of variola, in lesions caused by tartar emetic or croton oil, and in several forms of dermatitis. It is essentially microbian.
8th. Furunculus: Furuncle: Boil. Inflammatory nodosity of the derma, resulting in a necrotic central core and suppuration. Is bacteridian and common on the coronet and lower parts of the limbs in solipeds.
9th. Carbunculus: Carbuncle. An inflammatory nodosity or cluster of nodes of much greater extent, tending to necrotic change and sloughing over a much more extending area. Microbian.
10th. Squama: Scales: Dandruff. Exudation products and cells dessicate and exfoliate as branlike scales or thicker coherent laminæ. Examples are found in psoriasis, pityriasis, eczema, variola, rinderpest, etc.
11th. Crustæ: Crusts: Scabs. Hard, solidified masses of epidermis, blood, pus and serous exudate.
12th. Callositas: Callosity. Abnormal thickening of the epidermis, as a physiological protective cell growth. Examples: pads on the knees of camels, cows and even horses from kneeling on a hard, uneven surface.
13th. Sitfasts: Necrotic Callosities. Combination of dried up exudate of horny consistency, and a thickened, fibroid and partially necrotic portion of the subjacent derma with little or no disposition to spontaneous detachment.
14th. Cornu Cutaneum: Keracele: Horny Growth. Abnormal horny growth from keratogenous tissue, or from the derma in its vicinity or at some other point of the skin.
15th. Erosions: Abrasions. Lesions of the cuticle exposing the true skin, and the result of itching, scratching, friction, biting or other mechanical or thermic injury.
16th. Rimæ: Cracks: Chaps. These are linear breaches often confined to the epidermis in the bends of joints, under congestion and suppression of sebaceous secretion, in elephantiasis, dropsy, petechial fever, etc. Unless they have ulcerated they may heal without cicatrix.
17th. Crevasses: Fissures. These are chaps, which extend into the derma, giving rise to destruction of tissue and leaving a cicatrix on healing. Examples are found in the hollow of the pastern, behind the knee (Mallenders), in front of the hock (Sallanders), in the swellings of petechial fever, malignant catarrh, stocked legs, grease, etc.
18th. Ulcus: Ulcer. A sore that extends by the continual molecular breaking down of the forming granulations and of the adjacent and subjacent diseased tissue.
19th. Excrescences: Hyperplasiæ: Phymata: Dermatomata. These may include over luxuriant granulations which rise above the level of the skin and become organized into projecting fibro-cellular, raw or scabby masses: tumors of all kinds—warty, papillomatous, horny, epidermic, cancerous, sarcomatous, pigmentary, angeiomatous, tuberculosis, etc.
20th. Cicatrices: Scars. These are puckered, raised or sometimes depressed, lines or areas of condensed connective tissue with a covering of epidermis, taking the place of the normal dermis and epidermis and their appendages, which have been destroyed. They result from traumatic, ulcerous, or atrophic destruction of the skin.
21st. Neurosis. These may be exemplified by the intense itching of the skin without appreciable structural change. So in cutaneous anæsthesia and hyperæthesia.
22d. Modified Secretions. These include absence of perspiration—anidrosis, excessive perspiration—hyperidrosis, suppressed sebaceous secretion—asteatosis, excessive sebaceous secretion—steatorrhea or seborrhea, fœtid sweat—bromidrosis, colored sweat—chromidrosis, urinous sweat—uridrosis.
23d. Structural alterations in glands and ducts. Cystic ducts—hydrocystoma, blocked ducts—acne, inflamed glands—hidrosadenitis.
24th. Abnormal conditions of the hair. This embraces baldness, hypotrichosis, alopecia, excessive growth of hair, hypertrichosis, white patches, canities, nodular hairs, piedra, brittle hair, fragilitas crinium, felted hair, plica, trichoma.
25th. Scleroderma. Hard, leathery, thickened skin. Examples in old boars on shoulders, and in other animals.
26th. Elephantiasis Pachydermia. Enormous hypertrophy of the skin, with usually distention of the lymph plexuses and vessels (lymphangiectasis: see Vol. I).
26th. Vegetable parasites. Trichophyton, achorion, microsporon, actinomyces, etc. (See parasites).
27th. Animal parasites. Lice, fleas, diptera, trombidium, Acari, ixodes, cimex, filaria, coccidia, etc. (See parasites).