330 DISEASES OF CATTLE. 



toms. 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 charac- 

 terized 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 en- 

 circle 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 fat- 

 tened for beef, the meat being perfectly harmless to the consumer. 



PARASITIC DISEASES OF THE SKIN. 



RINGWOKM (TINEA TONSURANS AND TINEA FAVOSA). 



Ringworm is an affection of the skin, caused by a vegetable para- 

 site. 



The form known as tinea tonsurans is produced by the presence 

 of a minute or microscopic fungus — the Trichophiiton tonsvro.ns, 

 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, nucleated, and seldom vary 

 much in size. They are very abundant in the hair follicle. The fila- 

 ments 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 Avith exudation 

 occui's, followed by the formation of scaly, brittle crusts. The 

 patches aj^pear 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. A^ery early in the deA'ehipment 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 Achorton schonJeinii. 

 This enters the hair follicle and involves the cuticle surrounding it, 

 small crusts form which increase in diameter and thickness and then 

 l)ecome elevated at their margin, forming a cup-shaped scab, the 

 favus cup, which gives the disease its distinctive character. The 

 numljer of these cups A'aries from a few to many hundreds. The 

 haJis involved become lirittle and broken, fall off with the crusts, 

 leaving small bald jtatclies. The crusts are of a pale or sulphur- 

 yellow color at first; as they grow older they turn darker, or to a 



