MANGE. 



551 



a. Psor optes communis (in the horse, ox, and sheep). 



b. Psor optes euniculi (acari of the rabbit's ear). 



In all sub-species of psoropteS we find interesting morphological 

 variations ; Zahn has mentioned some in the horse ; we have also 

 seen them several times. 



C. The Symbiotes live especially upon the surface of the skin 

 of the extremities and exist on epidermic scabs. They are relatively 

 voluminous (0.3 to 0.5 millimetre); their outlines are visible to the 

 naked eye or with the magnifying glass ; the head is short and coni- 

 cal, wider than long ; the body is ovoid, slightly notched upou the 

 periphery ; the legs are long and the sucking cups are shaped like 

 a Roman shield ; in the male, they are found upon four pairs of 

 legs ; in the female, they are found upon the first, second, and 

 fourth pairs ; the male carries two copulating cups and the young 

 female two copulating tubercles. Zurn has established the follow- 

 ing division : 



a. Symbiotes communis, 



(1) Symbiotes equi et bovis, which occasion mange of the pastern 

 and tail. 



(2) Symbiotes avis, which produces mange of the sheep's leg. 



b. Symbiotes felis, canis, and euniculi (acari of ear mange).^ 

 General characters of the different Acari ; domestic 



ANIMALS UPON WHICH THEY ARE OBSERVED. From a clinical 

 standpoint, the three kinds of psoroptic acari produce as many 

 special manges, on account of the different biological conditions of 

 these parasites. 



1. Sarcoptic mange starts preferably upon the head and on the 

 regions which are imperfectly protected by hair or wool. In the 

 horse, dog, and pig, it often extends over the whole surface of the 

 body. In the dog its selected place is the base of the ears, the 

 joints, the lower pectoral region, the belly, and the internal side of 

 the extremities ; in the sheep it does not invade the parts which are 

 deprived of wool. 



2. Psoroptic mange is especially observed upon the protected 

 regions. In the horse it is mostly found upon the inner side of the 

 legs, the neighborhood of the sheath, at the base of the mane and 

 tail ; but when the hygiene of the skin is neglected, it may extend 

 over the actual surface of the body. In sheep it affects the parts 



' French authors distinguish only: in sarcoptes, /S'. scabiei and /S^. minor; in pso- 

 roptes, Ps. communis; in symbiotes, S. communis and S. auricular am. — n. d. t. 



