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XVII. On the Changes produced in Atmospheric Air, and Oxygen 
Gas, by Respiration. By W. Allen, Esq. F.R.S. and W 
H. Pepys, Esq. F. R. S. 
Read June 16'th, 1808. 
The process of respiration, or breathing, is so intimately con- 
nected with our existence in life, that from its first moments* 
to the final close, sleeping and waking, this necessary action 
is constantly maintained : nor can it be suspended even for a 
few minutes without considerable pain and the utmost danger. 
This important process has of course excited the curiosity both 
of ancient and modern philosophers ; among the latter we find 
the distinguished names of Mayow, Priestley, Goodwin, 
Menzies, Spallanzani, Scheele, Lavoisier and Davy, whose 
successive labours have thrown great light upon this difficult 
subject, and prepared the way for farther investigation ; but it 
is impossible to take a review of what has already been done, 
without perceiving that some important points were by no 
means satisfactorily settled ; an accurate method of separa- 
ting the different gasses, and ascertaining their exact proportion 
in any given mixture, was still a desideratum when many of 
the experiments were made, and it is only of late years that 
Eudiometry has attained its present perfection : the quantity 
of residual gas in the lungs after a forced expiration was a 
matter in dispute among former experimenters, some making 
it one hundred and nine cubic inches, and others only forty ; 
jvidcccviii. K k 
