303 
furnishing oxygen gas to supply its place. After ha- 
ving made a forced expiration, the operator began to 
respire oxygen, until nearly all the air, previously 
existing in the lungs, was expelled. This air, partly 
by experiment, and partly by calculation, was found, 
at temperature 53, to amount to 141 cubic inches, 
which consisted of 22.56 oxygen and carbonic acid, 
and 1 18.54 nitrogen. Hence, it is inferred, that, af- 
ter a forced expiration, the lungs of this person must 
have contained 141 cubic inches of air, which, at 
temperature 97, would be increased in bulk to 154 
cubic inches *. In another experiment of the same 
kind, the volume of air in the lungs is estimated at 
226 cubic inches, of which the oxygen and carbonic 
acid formed together about one-fifth f. 
600. The large portion of nitrogen gas, which thus 
appeared to exist in the lungs after the most forcible 
attempt at expiration, induced these chemists to re- 
peat their experiments on the respiration of oxygen 
gas. The experiment was made with 2668 cubic 
inches of oxygen, which contained four per cent, ni- 
trogen. The gas was breathed for 13 minutes, and 
was afterwards analysed. The total nitrogen in the 
gas inspired was 106.72; in that expired, 211.80? 
so that 105.08 cubic inches of nitrogen had been ob- 
tained from the residual air of the lungs. " The 
question, therefore, is, whether this increase of nitro- 
gen can be owing to the residual gas contained in the 
* Phil. Trans. 1808, p. <l66. 
t Ibid. p. 276. 
