Pi 
36 On Respiration and Animal Heat. 
they deduce a number of important. results. 
The first and the principal one is, that the quan- 
tity of carbonic acid gas emitted is exactly equal, 
bulk for bulk, to the oxygen consumed. This 
is the same conclusion as I had obtained ; it 
amounts almost to a demonstration, that the 
oxygen which disappears is spent wholly in 
the formation of carbonic acid; though it is 
possible to conceive that one half of the oxy- 
gen unites to carbonic oxide, from the lungs, 
and the other half to hydrogen, from the same 
source, thereby forming both carbonic acid 
and water, agreeable to the notion of Lavoi- 
sier and Crawford. 'This last position, how- 
ever, appears to me highly improbable. The 
authors do not produce any decisive experi- 
ments, nor give an opinion, respecting the 
question, whether the oxygen combines im- 
mediately with the carbone presented to it, as 
supposed by Crawford, or, on the other hand, 
the oxygen combines with the blood, and in 
the process of circulation, carbonic acid is 
formed, which is given out in the lungs, as 
La Grange and Hassenfratz would have it. 
Messrs. Allen and Pepys estimate the carbonic 
acid emitted in a day by a middle-sized man, 
to be about 3ilbs. troy. They establish a 
fact, that before was doubtful, viz. that in 
ordinary respiration no material absorption or 
