262 Messrs . Allen and Pepys on the Changes produced in 
than a minute he found himself obliged to take deeper and 
deeper inspirations ; and at last the efforts of the lungs to 
take in air became so strong and sudden, that the glass was 
in some danger of being broken against the side of the gaso- 
meter. A great sense of oppression and suffocation was now 
felt in the chest, vision became indistinct, and after the second 
minute his whole attention seemed to be withdrawn from 
surrounding objects and fixed upon the experiment. He now 
experienced that buzz in the ears which is noticed in breathing- 
nitrous oxide, and after the third minute had only sufficient 
recollection to close the cock after an expiration. This secured 
the result of the experiment ; but he became so perfectly in- 
sensible that, on recovering, he was much surprised at find- 
ing his friend and the assistant on the table in the act of sup- 
porting him. It was noticed that he made thirty-five inspi- 
rations during the experiment. We now examined the air 
which had been so treated. 
100 parts contained 10 carbonic acid, 
4 oxygen, 
86 azote, 
100 
In this experiment it is remarkable, that the air which had 
been so often through the lungs, should only have furnished 
10 per cent, of carbonic acid, while the air which passes them 
but once contains from 8 to 8.5. 
Here the oxygen had lost 7 from 21, and the azote had 
gained 7 upon 79. 
We knew by previous experiment,* that every cubic inch of 
* See the experiments on carbonic acid in the Society’s Transactions. 
