532 SUPPLEMENT 



I present the description here, is of a species different from 

 the one observed by that naturalist. It appears to me more 

 conformable to the species which the same author designates 

 by the name of Acarus exulcerans, judging merely by the 

 phrase which he applies to it, as he has given no other 

 description." 



Its eight feet are rather short, especially the first two pairs. 

 These last are thick, conical, have some hairs, of which a few 

 are tolerably long. These feet are terminated by a slender, 

 straight, cylindrical part, having at the end a little ball, in the 

 form of a vesicle, which the animal rests on the level on which 

 it walks, and guides in various directions. The four posterior 

 feet are equally terminated by a slender and brown part; but 

 Degeer could not perceive the vesicle of the preceding. These 

 posterior feet have a very long hair, and are placed at a cer- 

 tain distance from the first two pairs. When removed from 

 the epidermis, this little animal remains at first inactive, but 

 it moves its feet by degrees, and commences to walk, though 

 but slowly. 



Whether this mite be not that of the common human itch, 

 or whether Degeer has made his observations on individuals 

 of different forms, or did not study the subject with sufficient 

 attention, the figure which he gives of it does not accord with 

 that of the itch-mite published by Dr. Gales in a dissertation 

 of great research on this subject, and whose observations have 

 been confirmed by several celebrated naturalists. He had 

 the courage to inoculate himself with the itch by means of 

 this acarus. Other researches on this subject, made on divers 

 animals, have proved that the mites, taken from their wounds 

 when they were afflicted with this malady, differed from that 

 of the human itch. 



M. Latreille saw a quadruped of New Holland, (the 

 phascolomys) brought alive to Paris, where it died a few 

 days after, as it would seem, of the itch. The surface 



