398 ON THE CONTAGION OF ITCH OR MANGE. 
although they have deserted the spot they occupied two days 
before. Some ecchymotic spots, produced by the lesion made 
into the superficial vascular network, indicate the places where 
suction has been applied. 
10 th. — Grooves commenced and abandoned, demonstrate that 
the acarus are in search of some home to please them, whence 
they may find suction fit for their nutrition. Not one of the 
insects, though ordinarily so productive, has left any eggs 
behind it. 
1 5th. — Same observation. The insects are still living. The 
belly of the rabbit is covered with furfuraceous pellicles, but 
nowhere is to be found the true groove. 
1 st July. — The hair has grown, and no longer permits us 
to discover the insects. No eruption is to be seen, nor any 
sign of itch. The rabbit continued well during July and August, 
notwithstanding, altogether, it has received fourteen acarus. 
Transmission from Man to the Cat. 
A cat was placed under experiment at the same time, during 
the very same days, with the rabbit. Fifteen acarus disappeared 
upon her skin without our being able to find them again. It is 
true that, less enduring than the rabbit, she did not permit us 
to use the razor. This cat, which lived at the hospital Saint 
Louis, never once created any suspicion that she felt the insects 
upon her. 
Transmission to Birds. 
Fifteen acarus were placed at three different times, at intervals 
of ten days, underneath the wings and feathers of a sparrow, 
which never experienced the slightest irritation or annoyance. 
The same experiment was made upon a Guinea-pig and upon 
a rat, without affording any result. 
Conclusions. 
It may therefore be deduced from these divers observations, 
that the insect of the itch of man is able to survive for some 
variable time upon animals; that it conceals itself at once un- 
derneath their epidermis, without making grooves through it ; 
a circumstance ascribable in the one case to the fineness of the 
epidermis, which becomes detached in scab as the insect bur- 
rows under it ; in the other case, to the quality of the nutritious 
juices, which, although fit for sustenance for a certain period of 
the life of the acarus, and especially in the rabbit, is not suffi- 
ciently grateful to detain them in one place, like that of man. 
