PARASITES AND SKIN DISEASES 115 



be made only upon the discovery and rqeogni- 

 tion of the parasite. 



In order to determine the presence of tl^e 

 parasite it is necessary to get a deep scraping 

 of the skin. . This can be done by first of all 

 removing superficial scales and debris and then 

 with & blunt knife scraping the skin until blood 

 oozes. The material thus obtained is now 

 boiled for ten niinutes in a ten per cent solution 

 of potassium hydroxid and allowed to settle -^ 

 or is centrifuged. The supernatant fluid is de- 

 canted off and the residue transferred to slides 

 and examined microscopically under loisv mag- 

 nification. . . 



Symptorfis. — The symptoms are essentially 

 those of a dermatitis, manifested by irritation, 

 reddening and thickening of the skin, desqua- 

 mation of epithelium and, loss of hair. The 

 pruritis is intense and the animal inflicts con- 

 siderable damage to the skin by its persistent 

 rubbing and scratching. 



In an advanced case the primary skin.lesioiis 

 are . entirely masked by those resulting from 

 self-inflicted injuries, but if seen in the early 

 stages the skin is seen to be covered with little 

 red papules, somewhat like |lea bites ; these 

 exiide a drop of serum and the hairs become 

 matted together. Later patches of skin be- 

 come bald, covered with scales and very much 

 thickened. Desquamation and piling up of the 



