Sf:riV DISEASES. 27 g 



are more easily disposed of. Another species — demociex — in- 

 habits the sebaceous glands of the skin in sheep and dog, and 

 causes much irritation with acne like eruption. Among acari 

 occasionally parasitic may be mentioned :— The dernMuyssiis 

 (misnamed hen louse), the gamasus of musty hay, and the leptus 

 (misnamed jigger in the Western States of America), all, except- 

 ing the last, living on the surface and easily discovered. Lastly 

 a tyroglyph is accidentally parasitic on all domestic animals. 



Of the sarcoptes there is one species lives on the horse, which 

 will temporarily inhabit the skin of nun ; a second is peculiar 

 to the goat ; a third is common to dogs and swine ; a fourth to 

 cats and rabbits ; and a fifth to chickens, horses, and foxes. 



One species of dermatophagus lives on the heels and legs of 

 horses, another on the tail, neck, etc., of cattle, and a third on 

 the pastern, limbs, and less frequently the trunk of sheep. 



Of dennatocoptcs there is also a particular species for each 

 of these animals — horse, ox, and sheep— though usually con- 

 founded with each other. These are the most common causes 

 of mange, and from their non-burrowing habits are most easily 

 disposed of. 



Accessory causes. — Though the reception of the acarus is the 

 one essential cause of mange, yet others conduce to its speedy 

 diffusion — as poor condition, filth, and warm seasons. Some 

 acari, like the derruatop/iagi, may even seem to suspend opera- 

 tions in winter, and cause little or no trouble until the following 

 spring. 



Symptoms. — We must state these in general terms, throwing 

 the whole class into one group. There is intense uncontrollable 

 itching, aggravated by hot weather or buildings, and by per- 

 spiration. If the affected part is scratched the animal shows 

 his gratification by moving his body as if rubbing, and especially 

 (in horses) by a nibbling movement of the lips. In sheep the 

 wool is torn off, and white tufts hang on the dark surface of the 

 fleece. The skin is thickened and rendered rigid by exudation 



