DISEASES OF THE OX AND SHEEP. 



437 



SCABIES IN SHEEP. 

 The aflfliction known as scabies is one of very wide and far- 

 reaching importance. The value of the sheep consists in great 

 part of the fleece, and, as all sheep-farmers know, the disorder 

 generally known as sheep-scab works an immense amount of 

 havoc not only with the fleece, but also with the animal itself. 

 It appears that there are three distinct forms of scabies, 



Fig. 56. — The Dermatodectes ovis. 



namely, the Psoroptic, the Sarcoptio, and the Symbiotic 

 varieties. Of these the first is by far the most common, and 

 it seems to be the only kind which has been recognised in this 

 country. Hence we shall deal with the psoroptic variety 

 only. 



In the first place, it may be said that it is occasioned by 

 the ravages brought about by the little creature known as the 



