172 



DISEASES OF 



The most common form is where the mode of growth 

 of the fungi is in the form of circles of greater or less 

 regularity. These fungi attach themselves to the skin 

 and burrow down into the sheaths of the hairs, causing 

 more or less irritation and inflammation. They live and 

 develop by absorbing the nutritive elements of the 

 skin. Young animals or those poorly nourished are 

 more frequently the subjects of the disease than older 

 and stronger animals. In calves it is found most fre- 

 quently on the eyelids and lips and skin of the neck ; 

 rarely on the hind limbs. In horses it is most frequent- 

 ly found in the region of the root of the tail, and seems 

 to be caused in many cases by the crupper of the har- 

 ness carrying the spores or germs of the disease. It is 

 quite common in dogs, and may occur in any part of 

 the body, causing an intolerable itching. 



Fig. 62. Microscopic appearance of parasite causing ringworm in poultry, 



