and Oxygen Gas ly Respiration. 243 



-merits, to the final close, sleeping and waking, this neces- 

 sary action is constantly maintained : nor can it be suspend- 

 ed even for a few minutes without considerable pain and the 

 •inmost danger. This important process has of course ex- 

 cited the curiosity both of ancient and modern philosophers ; 

 among the latter we find thedistinguished 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 further 

 investigation^ but it is impossible to take a review of what 

 has already been done, without perceiving that some im- 

 portant points were by no means satisfactorily settled ; an 

 accurate method of separating the different gases, and as- 

 certaining their exact proportion in any given mixture, was 

 £tilj a desideratum when many of the experiments were 

 made, and it is only of late years that eudiometry has at- 

 tained 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 hun- 

 dred and nine cubic inches, and others only forty ; and 

 yet it is of the utmost consequence in all calculations upon 

 the effects produced, especially upon small portions of gas, 

 that the state of the lungs should be accurately determi- 

 ned ; this constitutes the great difficulty in the investiga- 

 tions. We therefore commenced our labours by construct- 

 ing an apparatus, in which we are able to respire from three 

 to four thousand cubic inches of gas, conceiving, that in this 

 quantity, the error arising from the residual gas in the lungs 

 must be so much obviated as to permit the most satisfactory 

 results. 



The apparatus consists of three gasometers, two of which 

 are filled with mercury, and one with distilled water. 



The' water gasometer which belongs to the Royal Institu- 

 tion, is capable of holding four thousand two hundred cubic 

 inches of gas, and each of the mercurial ones three hundred 

 cubic inches : the apparatus was so arranged that the inspi- 

 rations were all made from the water gasometer, andthe ex- 

 pirations into the mercurial gasometers alternately. Each of 

 the gasometers is furnished with a graduated seale^ and they 



O 2 are 



