277 
riment, amounted only to 23 cubic inches. One 
hundred parts of the respired air afforded, on analysis, 
8.5 carbonic acid, 12.5 oxygen, and 79 nitrogen gas*. 
The experiment was repeated several times ; and in 
one instance, 9890 cubic inches of air were breathed 
for 244 minutes, with the loss of only 18 cubic in- 
ches, and 1OO parts of the expired air then afforded, 
on analysis, 8 carbonic acid, 13 oxygen, and 79 nit- 
rogen f. 
567. Now the air employed in these experiments 
contained, in 100 parts, 21 oxygen and 79 nitrogen; 
and, in the numerous analyses which were made of 
this air after its respiration, the portion of oxygen 
that disappeared was exactly replaced by that of car- 
bonic acid produced ; so that, in every instance, these 
two gases formed together -iVs- of the respired air, 
the remaining 79 parts being pure nitrogen gas. It 
is, therefore, concluded, " that the quantity of car- 
bonic acid gas emitted is exactly equal, bulk for bulk, 
to the oxygen consumed J." 
068. In subsequent experiments on the respiration of 
a Guinea pig, these chemists found, that when 310 cu- 
bic inches of atmospheric ahvwere breathed for 25 
minutes by this animal, its volume experienced no 
variation whatever, and the portion of its oxygen, 
which disappeared, was replaced by an equal bulk 
of carbonic acid ; wherefore, they justly conclude, 
" that when atmospheric air alone is respired, even 
* Phil. Trans. 1808, p. 254. 
t Ibid. p. 257. I lb. p. -?7 
Ibid. 1809, p. 414. 
