MITES. 199 



multiply with such enormoua rapidity that it is easy 

 to understand how a single fertilized female, trans- 

 ferred to a new host by contact with an affected 

 animal, is able, in a short time, to make large patches 

 of the skin mangy. The course of the disease is 

 generally as follows: — Soon after infection small 

 swellings appear, which become little bladders of the 

 size of a pin's head. These burst, and the affected 

 parts of the skin are quickly covered with a crust 

 formed from shrivelled bits of skin and dried-up fluid. 

 In many places the attacked parts of the skin are 

 moist, for the host, in consequence of the severe 

 itching, rubs or knocks itself. In consequence of the 

 shedding of fluid the hairs stick together, and later on 

 fall out. The skin thickens, becomes encrusted, and 

 is thrown into folds, between which there are deep 

 cracks. Among domesticated animals the sheep is 

 certainly the one which suffers most from scabies 

 (Bermatocoptes), especially as the disease spreads 

 rapidly in the warm sheltering fleece, which also 

 makes the removal of the parasites a matter of the 

 greatest difficulty. The wool gets dry and brittle in 

 the diseased parts, and its fibres become loose, though 

 they remain attached for a short time, since their tips 

 are glued together by the sticky substance which 

 exudes from the little thickenings in the skin. They 

 gradually fall out, however, leaving the skin covered 

 with a thick brownish crust, looking as if it were 

 soaked with oil. Badly infested sheep get thin and 

 even die. This, however, is not usually the case, and 

 the injury consists in the great deterioration of the 

 wool, both as regards quantity and quality. 



The following summarizes the kinds of scabies 

 affecting man and domestic animals, and indicates 

 how far one kind of host can affect another : — ■ 



Itch of Man {Sarcoptes) can be caught by the dog, 

 but by no other domestic animal. 



Scabies of the Horse. — The sarcoptes mange of this 



