Messrs. Allen and Pepys on Respiration. 421 
From the results of these experiments, it seemed that when 
the usual proportion of azote was not present in the gas re- 
spired, there was a disposition in the blood to give out a cer- 
tain quantity in exchange for an equal volume of oxygen, and 
we resolved to try, whether this circumstance would occur 
when hydrogen was substituted for azote, we accordingly 
made a mixture containing 22 per cent, oxygen and 78 hy- 
drogen. 
Experiment 6. Hydrogen and Oxygen. 
The pig employed in the last experiment, was placed upon the 
stand in the glass A, with 66 cubic inches of common air as usual . 
250 cubic inches of the mixture were passed from the gaso- 
meter, communicating with B through the glass A into the 
gasometer communicating with C during sixteen minutes. 
The animal did not appear uneasy : a second quantity of 250 
cubic inches was passed in seventeen minutes and three quar- 
ters : the animal did not seem to be in the least incommoded. 
A third quantity of 250 cubic inches was passed, in about 
sixteen minutes. 
And a fourth quantity of 250 cubic inches in eleven minutes 
and three quarters ; but during this time, the animal became 
very sleepy, and towards the end of the experiment, kept his 
eyes constantly shut ; he, however, appeared to suffer nothing, 
and was easily roused for a short time by rapping at the side 
of the glass. At the end of sixty one minutes and a half, he 
was taken out, and we found that during this time, he had 
produced 60,20 cubic inches of carbonic acid gas, or rather 
less than one cubic inch in a minute. 
It appears, that less carbonic acid was evolved in this in- 
stance in a given time, than when oxygen was respired, but 
MDCCCIX, 3 I 
