On Respiration and Animal Heat. $1 
the acid. On thissupposition, the oxygen would 
be sufficient for both; and we must consider a 
triple compound of carbone, hydrogen, and. 
oxygen, to transude through the lungs, which is 
' to be converted ito carbonic acid and water. 
This explanation would not differ essentially 
from that given by Lavoisier and Crawford ; 
which supposes that nothing enters the blood 
in respiration ; but that the combustible mat- 
ter unites with oxygen on the surface of the 
lungs. The position seems to require that 
whenever carbonic acid is generated in the 
lungs, a certain portion of water must be 
generated at the same time; I doubt whether 
this is consistent with facts. It is well known 
a person may, for some time, breathe with 
impunity, air containing more aqueous vapour 
than that ordinarily expired; yet carbonic 
acid continues to be formed nearly as usual. 
I have been for 10 minutes in a stove where 
the temperature was 140°, and where the 
vapour inspired was more abundant than that 
expired ; yet the air expired at the conclusion 
of that time contained 3 per cent. of carbonic 
acid, and had lost 4 per cent. of oxygen, 
nearly as usual; and no superabundance of 
vapour was perceived on the lungs. Having 
made some comparative trials upon air that 
has been breathed, and air in which charcoal 
