320 
all cases, in accordance with their own experience ; 
for, in one instance, where atmospheric air was re- 
spired for five minutes and a half, the quantity of car- 
bonic acid is stated tohaveamounted to 51 cubic inches 
per minute; and the faster respiration was performed, 
the more carbonic acid, it is said, was given off, and 
consequently the more oxygen was consumed*. Indeed, 
it is reasonable to expect, that, within certain limits, 
a variation in the condition of the respiratory organs, 
or in the exercise of their functions, should occasion 
a corresponding variation in the products obtained ; 
but the facts just stated shew, that, if rhe respiration 
be sufficiently rapid,, as much, or more, carbonic 
acid can be formed from common air than from pure 
oxygen gas ; and therefore, the production of 
that acid is not so much regulated by the abundance 
of oxygen in the air inspired, as by some other es* 
sential condition of the animal organs. 
620. With respect to the actual consumption of 
oxygen, these chemists conclude, that the atmosphe- 
ric air, expelled from the lungs, usually contains 
from 8 to 8.5 per cent, of carbonic acid, and that the 
proportion of acid in no case exceeds ten per cent. 
They estimate the quantity of acid thrown off in ele- 
ven minutes at 302 cubic inches, which is about 
27-45 per minute ; and supposing the production 
uniform for twenty-four hours, the total quantity in 
that period would be 39534 cubic inches, weighing 
186S3 grains; the carbon in which is 5363 grains, 
or rather more than eleven ounces troy. The oxy- 
* Phil. Trims. 1808, p. 25? 
