260 Messrs. Allen and Pepys on the Changes produced in 
proved to contain only from three to five per cent. ; conse- 
quently the last portions must contain more than appears by 
the average ; that is, more than q.5 per cent. 
It now appeared to us of consequence to ascertain exactly 
what happened to a given volume of atmospheric air, when it 
was inspired and expired as often as possible. 
Fourteenth Experiment 
Three hundred cubic inches of atmospheric air were ad- 
mitted into the mercurial gasometer G. 1 . ; the other, G. 2, 
was empty. The nose being properly secured, and the mouth 
applied to the tube A, as usual, air was drawn from G. 1, and 
by half turning the cock, 2, was expired into G. 2. This 
was repeated until the contents of G. 1 had been made to 
pass through the lungs, and transmitted to G. 2. The air 
was then inspired from G. 2, and expired into G. 1, until 
G. 2 was nearly empty. This was repeated about eight or 
ten times during three minutes, until respiration became ex- 
tremely laborious, and the operator desisted. 
The whole 300 cubic inches must have passed eight or ten 
times through the lungs ; and we confidently expected, that 
on examining the air we should have found an unusual pro- 
portion of carbonic acid. 
But 100 parts gave only g.g carbonic acid 
55 oxygen 
' 
85. azote. 
ICO 
* In this experiment there was obviously no occasion to make allowance for the 
air contained in the tubes and sockets. We find its volume to be eighteen cubic 
inches. 
