\S13.] emitted from the Lungs during Respiration. 32$ 



operation of different external circumstances, affects the air in 

 very different degrees. — The circumstances which have been 

 discovered to influence the chemical effects of respiration are, 

 the temperature of the air respired, the degree of muscular 

 exertion, the state of the digestive organs, and the condition of 

 the system ay affected by fever." Dr. B. continues: " It is 

 highly probable that other circumstances will be discovered by 

 multiplying and varying our experiments upon the living body,** 

 and informs us, that " these different affections of respiration 

 will undergo a farther examination in the third part of his essay.'* 

 Now this, 1 believe, has never been published ; whether, there- 

 fore, he, or any other person, has anticipitated me in what 1 am 

 about to offer, I am unable to determine : if so, my experi- 

 ments will at least have the effect of corroborating theirs ; and 

 if not, their interesting results may possibly induce some one to 

 repeat them, and thus either confirm their accuracy, or point 

 out their errors. 



Mr. Brande, also, in a paper on respiration, after having 

 noticed the above circumstances in a general way, says, " the 

 proportion, however, (of carbonic acid) varies in the same indi- 

 vidual during the 24 hours, for I have found the quantity of 

 carbonic acid gas emitted from my own lungs to be rather less 

 in the morning than towards the evening ; but this also varies in 

 different people."t It may also be mentioned, that Messrs. 

 Allan and Pepys, in their excellent paper on this function, found 

 the quantity formed by the same animal during sleep to be less 

 than when waking. J 



Such then, with perhaps a few other general facts of a similar 



kind, constituted the whole of our knowledge (or rather of 



mine) respecting this most important part of the phenomena of 



respiration, and this, together with some other reasons which 



will be shortly known to the public, induced me to think of 



undertaking a set of experiments with the hope of throwing 



sonic light upon the subject, and, if possible, to find out the 



laws which it obeyed. With this view, having contrived a 



simple apparatus, by means of which I could easily, and with 



considerable accuracy, analyze the respired air, I put myself 



upon a sort of regimen, which consisted in keeping myself as 



nearly as possible in the same state in every respect, and thus 



commenced the arduous task. To this plan I adhered as nearly 



as circumstances would permit for upwards of three weeks, 



making the experiments every hour, and sometimes oftener, 



during the day, and occasionally during the night also. Now 



the results obtained from this great mase of evidence, amounting 



• Bauy on Respiration, p. 78. + NIch. Journal, vol. xi. 



I Phil, Troni. |80Q, Nich, Jour, vol, WT, 



