THE SKIN. 



357 



Animal Parasitic Diseases of the Shin of Cattle. 



Mange — Acaeiasis — is a contagious disorder due to tlie 

 presence and ravages of those Araclinidan or spider-like 

 parasites generally known as the Acarus hovis, which 

 comprises two forms (according to Gerlach)_, Bermato- 

 dectes hovis and Symohiotes hovis. Of these, the former is 

 most frequent, the latter being rare. Mange of the ox 

 is, therefore, due to Dermatodectes, which lives on the 

 surface of the epidermis, but gives rise to much irritation 

 by biting. Its most frequent seat is on the withers and 

 the root of the tail, but this preference is not very marked. 

 From the parts primarily affected the disease extends, and 

 passes through its various stages, during the more acute 

 of which there is intense itching. Circumscribed nodular 



Fig. 68. — Mange insects {Acarus hovis). (Dobson.) 



projections (papules) first appear; these become vesicles 

 and burst, giving exit to a watery fluid, which soon dries on 



