ABSORPTION OF NITROGEN. ^ 45 



amount is fomewhat lefs than has been ftated by Davy, who 

 makes it equal to about 5 c. inches per minute. Yet I am 

 inch'ned to think, that this is more a difference in appearance 

 than reality ; for if we confider that the moll; of Davy's ex- 

 periments give the refult of the changes produced on the air 

 by a fingle infpiration, or by a fmall number of refpirations, 

 while in the experiments juft defcribed, a large portion of air 

 was breathed for a confiderable length of time, fo as to be- 

 come, at laft, unfit for the due performance of refpiration ; 

 it is probable that the blood could no longer produce tl]e fame 

 alterations in its properties, that took place when a purer 

 atmofphere was infpired. It is alfo natural to fuppofe, that 

 the quantity of air confumed in refpiration varies in different 

 perfons, and in the fame perfon at different titnes. An ap- 

 proximation to the truth, therefore, is all that we can expe6l 

 to obtain in the determination of this queftion ; and we muft 

 reft fatisfied with the knowledge of the important fa6t, that 

 nitrogen is abforbed by the human body in refpiration. 



Theftriking uniformity in the analyfis of the atmofpherical Dr- Thompfon 

 air, by means of the fulphuret of lime, occurred alfo, as I phuiet'of lime'a 

 have wiih pleafure obferved, tp Dr. Thompfon in the nu- very excellent 

 merous trials which he has made on this fubje6t ; and furnifhes^^'^* 

 a mofl interefting problem for the inveftigation of the chemifl 

 and natural philofopher. 



I am, with much Refpeid, 

 Sir, 



Your raoft obedient Servant, 



AL. HENDERSON, M. D. 



r.dinb'irirh, 

 Jp-il i2, 1804.. 



Obftrvations 



