SCABIES. 



711 



SCAB IN SHEEP. 



Three forms of scab are described, viz., the sarcoptic, dermato- 

 dectic, and symbiotic. The dermatodectic or psoroptic is tlie 

 common form known in this country ; it is intensely contagious, 



Fig. 133. — Dermatodectes ovis. — (Gerlach.) 



and spreads with great rapidity, the parasite which causes it 



