THE SKIN 



399 



water bandages round the horn, keeping them constantly moist, 

 and at the same time administer a good dose of purgative medicine. 



PARASITIC DISEASES OF THE SKIN. 



678. Mange or Scab affects the horse, cow, sheep, dog, cat, 

 etc., and also the human being. This troublesome disease is due to 



m/j* 



Fig. 16. — Mature Female Acarus (Brown). 



the presence of small parasites developed from eggs, which are 

 deposited in vast numbers on or in the skin. 



679. These parasites are of three different families — viz. : 



1. Symbiotes — the parasites that live on the skin. 



2. Dermatodectes — those boring into the skin. 



3. Sarcoptes — those burrowing through the skin. 



These differ in size and form in the various animals — as may be 

 seen by the illustrations {Plate XL.)— and they also differ in a like 

 respect, according to the situation they occupy on the skin of the 



