26^ Messrs. Allen and Pepys on the Changes produced in 
azote ; and on reflection, it occurred to us, that if a certain 
proportion of oxygen had been absorbed or lost in any way, 
while the azote, remained unaltered, there must be an increased 
proportion of the latter. 
Now we knew exactly both the bulk and the constitution 
of the air before the experiment ; but it was impossible to 
know the bulk or volume after the experiment otherwise than 
by calculation. 
The 300 cubic inches of atmospheric air before the experi- 
ment contained 21 oxygen, 79 azote in 100 parts, making the 
total quantity of oxygen 63 cubic inches, 
azote 237 
300 
Now if the lungs be capable of fixing permanently any 
azote from the atmosphere, it appears by our experiments 
that the quantity must be very minute, seeing that in the 
11th, 12th, and 13th experiment, it did not disturb the pro- 
portion of azote, as shewn by the eudiometer ; we shall there- 
fore in the present instance assume the volume of azote after 
the experiment at 237 cubic inches, as before. 
But after the experiment, every 100 parts consisted of 
86 parts azote, and 14 oxygen, either in the form of carbonic 
acid, or free. 
86 : 14 :: 237 : 38.58. 
Therefore the total quantity of oxygen left after the experi- 
ment would have been 38.58 cubic inches. 
Then 237 azote -j- 38.58 oxygen = 275.58 ; 
the quantity of gas after respiration would therefore have 
been 275.58 cubic inches. 
300 — 275.58 = the loss of oxygen, or 24.42 cubic inches. 
