DISEASES OF THE SKIN. 



709^ 



The itching whicTi they cause is not so severe as in the other 

 two forms, and they are much more stationary than the derma- 

 todectes, the bites of ■which cause an exudation and a thicken- 

 ing of the epidermis, which defies the further action of their 

 mandibles, and compels them to attack the surrounding healthy 

 skin. 



Two parasites seem to infest the legs of horses, viz., the one 

 above described and the sarcoptes hippodus, described at page 

 677. Fig. 117. 



To complete the diagnosis, the presence of the parasites must 

 be determined, see Figs. 128, 129, and 130, it being remembered 

 that the sarcoptic variety, owing to the fact that the female 

 parasites preponderate very largely, are unsociable in their 

 habits, are fond of wandering, are more contagious than the der- 

 inatodectie, and much more so than the symbiotic^ 



MANGE IN THE OX. 



Two kinds of mites have been discovered in the^mange of 

 liorned cattle : — -'(1.) The Dermatodectes ; and (2.) Symbiotes 

 jjovis, which was first observed by Gohier, upon Hungarian oxen- 



FiQ.. 131 i— Dermatodectes bovia. — (Gkblaoh.) 



