412 Messrs . Allen and Pepys on Respiration. 
therefore be 108 cubic inches ; but the mean of our experi- 
ments would make it 183. 
Experiment 1. 141 
2- 225 
3. 23b 
4 - 133 
4)735 
183 
we are then almost compelled to allow that when pure 
oxygen is respired, a portion of azote is given off from the 
blood. 
We now resolved to perform a series of experiments 
upon some animal which lived wholly upon vegetable food, 
and made choice of the Guinea pig as one of the most ma- 
nageable. 
The apparatus consisted of our two large mercurial gaso- 
meters, which were made to communicate with a strong 
trough E, in the middle of which a small mahogany table D 
was made fast by a screw, for the purpose of supporting the 
animal under the bell-glass A, two holes were made through 
the table for the insertion of tubes to supply, and take off the 
air, each of them communicated with one of the mercurial 
gasometers ; the tube B delivered gas towards the upper part 
of the glass A, in order to bring the supply of fresh air near 
the head of the animal : the opening of the tube C was placed 
within half an inch of the table to convey off the respired air ; 
the gasometer connected with this tube, was made to commu- 
nicate with a mercurial bath G, in which portions of the re- 
spired air were preserved for examination. Quicksilver being 
