On Respiration and Animal Heat. 285 
the system, one is evident, namely, its con« 
tributing to the support of temperature in the 
same way as oxygen does, 
Since the late improvements in Eudiometry, 
attempts have been made to determine with 
greater precision, the changes effected by re« 
spiration:in the elastic fluids. It is obviously 
of im»vortance to learn the precise quantities of 
oxygenous gas inspired and expired, together 
_ with the quantities of carbonic acid, and aque- 
eus vapour expelled from the lungs. With 
respect to oxygen and carbonic acid, my own 
experience concurs with that of the generality 
who have carefully investigated the subject ; 
more in bulk of oxygenous gas is consumed 
than that of carbonic acid generated; the 
former appears to be about 5 per cent. upon 
all the gas inspired; the latter about 4 per 
cent. upon all the gas expired. It is very 
desirable, but at the same time very difficult, 
to determine the ratio more exactly. It ought 
to be observed too, that the quantities above 
specified are the medium for each one natural 
expiration; if the gas at the first moment of 
expiration be caught, it will be feund to con- 
tain about 3 per cent. acid, and to have lost 4 
of oxygen ; but if the last portion be examined, 
it usually contains 5 of acid, and wants 6 or 
more of oxygen; by taking the last gas of a 
D 
