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 was shown later that he had palmed off a common 
cheese-mite for the itch-mite. Many physicians 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 way by 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. Burrowing-mites (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, however, may again disappear 
without the application of remedies. 
These mites have a round or slightly oval body, a short 
beak margined by two cheeks, short, thick and conical legs, 
of which the two 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 Iteh-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 gnawing 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 
