Injurious to Man. 1 5 



Instances of this kind are, however, very rare, and Neumann 

 says that persons attending to dogs suffering from demodic 

 mange do not contract the complaint even if no precautions are 

 taken. Moreover, several experimenters have attempted to 

 transmit this parasite from dogs to human beings, without result. 

 It is exceedingly difficult, however, to transmit Demodex canimis 

 from diseased to healthy dogs. 



Demodex equi, Kailliet. 



Gaston Urbain has recently described a case in which 

 Demodex equi is supposed to have been transmitted to a human 

 being in Brazil, but the evidence which he gives on this point is 

 far from conclusive. 



Sub-Order— ASTIGMATA. 



Minute whitish or pale mites, without tracheae or stigmata. 

 The mandibles are chelate and the palpi short. These mites are 

 mostly oval in shape and convex dorsally. The Sarcoptidae (Itch 

 Mites) and Tyroglyphidae (Cheese Mites, etc.) are placed in this 

 suborder, which also contains the Feather Mites (Analgesidae), and 

 one or two other families. 



Family— SARCOPTIDAE. 



Sarcoptes scabiei, L. 



The Itch-Mite. 



Owing to the troublesome nature of the skin-complaint of 

 which it is the cause, the Itch-mite has attracted a good deal of 

 attention. The disease due to this parasite can be recognized by 

 the presence of the gallery or furrow which it constructs in the 

 skin. This gallery is rarely straight, being usually irregular and 

 sinuous, and varies in length, but may measure up to half an inch 

 or even more. It is sometimes very difficult to see in clean people, 

 but if a little ink is applied to the skin it runs in and helps to show 

 its track. Each of the galleries contains a single adult female 

 mite, and usually also a number of eggs in various stages of 

 development, as well as numerous little black points which are 

 the excrement of the Acarus (Fig. 5). Conical pustules, which are 

 another feature of this disease, are often present above the furrows, 

 but the parasite is never found in them ; these pustules are 

 apparently caused by an irritant poison secreted by the Sarcoptes. 



