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.