- 
{il, cONFINED IN STAGNANT AIR. 103 
thing indeed was perceptible on opening the vef:- 
fels; and the odour was certainly foetid or ca- 
daverous. I have been fenfible of it in all my ex- 
periments, which are very numerous, even in 
thofe made on the fimalleft animals: fo that the 
exiftence of this vapour is not to be doubted, 
though it is not always vifible; either from the 
fmallnefs of the quantity, or becaufe it is of 
a dry nature which may prevent it from appear- 
ing under the form of an aqueous veil. 
It is inconteftible that thefe exhalations are the 
real caufe of the death of animals. Sig. Cigna 
endeavours to prove it by recurring to the refem- 
blance we remark between the phenomena ex- 
hibited by fluids evaporating in confined air and 
thofe feen in animals refpiring in clofe veflels, 
The evaporation he has obferved continues long- 
er in proportion to the fize of the veffels, and 
fills them fooner as the air is more rarified. Ani- 
mals are alfo fubjeét to thefe two conditions; 
they live longer as the quantity of confined air 
is greater, and perifh fooner as the air becomes 
rarer (1). 
Colle&ting fome of the refults hitherto given, 
and connecting them with thofe that I shall after- 
wards eftablifh, it feems eafy to prove this fac. 
We have feen that two circumftances accelerate 
G 4 the 
(x) Lib. cit.” 
