On Respiration and Animal Heal. 1% 
azotic gas, oxygenous gas, aqueous vapour, 
and a very small quantity, almost inappreci- 
able, of carbonic acid gas; that the air ez- 
ptred consists of azotic gas nearly the same as 
before, oxygenous gas diminished in quan- 
tity; and carbonic acid and aqueous vapour, 
both considerably increased in quantity; the 
temperature ef the expired ‘air, as is well 
known, is in most instances much superior to 
that of the inspired air. 
Lavoisier and Crawford, followed by many 
respectable writers, seem to maintain, that the 
basis of carburetted hydrogen gas transpires 
through the thin membranes of the lungs, from 
the blood, where, meeting with the oxygenous 
gas of the atmosphere, a chemical union of 
the carbone and hydrogen with the oxygen 
takes place, forming carbonic acid and aque- 
ous vapour; at the same moment, part of the 
heat of the oxygenous gas is given out, which, 
according to Crawford, enters the blood of 
increased capacity for heat, and consequently 
does not materially increase its temperature. 
This heat is again given out during the circu- 
lation, as has been observed, in order to sup- 
ply the waste from the body. 
In order to establish this explanation, it is 
necessary to shew, that the oxygen disappear- 
ing is just sufficient to form the carbonic acid 
c 2 
