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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. 
f Ihese 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 w 7 alks, 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 wdiether Degeer has made his observations bn individuals 
of different forms, or did not study the subject with sufficient 
attention, the figure which he gives of it does not accord w 7 ith 
that of the itch-mite published by Dr. Gales in a dissertation 
of great research on this subject, and wdiose 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 W’ere afflicted with this malady, differed from that 
of the human itch. 
M. Latreille saw a quadruped of New 7 Holland, (the 
phascolomys) brought alive to Paris, where it died a lew 
days after, as it would seem, of the itch. The surface 
