52 BURROWING-MITES. 



duce this mysterious being, until at last a certain doctor 

 Gales mystified and tricked the Academy and pocketed the 

 prize. He showed to a medical commission selected for this 

 purpose, a mite which he claimed to have taken directly from 

 a patient suffering with the itch. He was awarded the prize, 

 and received in addition to it a medal for his great discov- 

 ery; it w^as showm later that he had palmed off a common 

 cheese-mite for the itch-mite. Many phA'sicians searched for 

 the mite in vain, mislead by the book in which Gales had 

 the audacity to publish descriptions of the parasite. In 

 1829 another prize was offered by Lugol, and a student of 

 medicine, Renucci, showed at last in 1834 a wa3' hj which 

 it could be found. He simply utilized a method used in Cor- 

 sica and elsewhere to kill the mites by removing them with 

 a needle. 



We can distinguish three groups of itch-mites: 



1. Burrowiiig-inites (Sarcoptes), which make tun- 

 nels in the skins of their hosts and which live by sucking 

 blood. All members of this group can successfully migrate 

 from an infested animal to man, and cause upon this new 

 host the itch, which disease, how^ever, may again disappear 

 without the application of remedies. 



These mites have a round or slighth' oval body, a short 

 beak margined by two cheeks, short, thick and conical legs, 

 of which the tw^o posterior ones are quite or nearly con- 

 cealed beneath the abdomen; the tarsus has often an am- 

 bulacrous sucker in the form of a simple and somewhat long 

 pedicel; the male possesses usually no copulatory suckers 

 and never has abdominal lobes. 



2. Skin-eating' Itch-mites (Psoroptes), which live 

 only upon the surface of the skins of their hosts, or among 

 the crust they form by irritating the skin, and -which feed 

 upon young epidermal cells by gna-^dng the upper surface of 

 the skin and hairs. Such mites, if they reach the skin of 

 man, do not cause the itch. 



These mites have the body oval; the beak conical, elon- 

 gated and destitute of cheeks; the legs are thick, especially 

 the front ones, and all are visible beyond the sides of the 



