132 CIRCULATING FLUIDS : 



their densities; consequently^ 1"17585 volume of oxygen is 

 absorbed for one volume of expired carbonic acid. Comparison 

 of the figures shows us that the mixture of the two gases in 

 respiration takes place entirely according to the law of diffusion 

 of gases ; for the most accurate method of experimenting gave 

 results^ in which the figures obtained for the carbonic acid and 

 absorbed oxygen, almost exactly agreed with those reckoned 

 according to the law of the diffusion of gases : 



In respiration, Avhich is thus a purely mechanical process, 

 the inspired air is first warmed to 99°"5, and saturated with 

 moisture at this temperature, which is rapidly accomplished on 

 account of its extensive distribution. It then experiences a sim- 

 ple diffusion; the nitrogen remains entirely unaffected; 1*1742 

 volume of oxygen is absorbed, and replaced by 1 volume of car- 

 bonic acid which is expired ; or for each volume of oxygen ab- 

 sorbed -8516 volume of carbonic acid appears. In consequence of 

 the accuracy with which the law of dift'usion is here observed, the 

 most minute portion only of other gases is absorbed or expired. 



That hydrogen, carburetted hydrogen, and carbonic oxide 

 gases are not contained in the expired air, the authors have 

 shown by some direct experiments ; but small quantities of 

 organic matters are evolved during respu'atiou, as is shown by 

 sulphuric acid, through which expired air has been made to 

 pass, being always coloured red.] ' 



Various opinions have been promulgated respecting the 

 formation of carbonic acid in the blood. The most natural and 

 probable is that of Lagrange and Hassenfratz, who maintain 

 that the blood takes up oxygen in the lungs and retains it in a 



' [For further information on this subject, the reader is referred to Valentin's 

 Lehrlmch der Physiologic, 1844, vol. 1, pp. 507-580, or to an excellent abstract 

 that appeared in the Chemical Gazette.] 



