THEORY OF RESPIRATION. 273 



vol. i. p. 345), and that this quantity of blood mea- 

 sures 320 cubic inches, then 1 cubic inch of oxygen 

 unites with 9 cubic inches of blood, very nearly. 



According to the researches of Denis, Richardson, 

 and Nasse (Handworterbuch der Physiologie, vol. i. 

 p. 1 38), 10,000 parts of blood contain 8 parts of per- 

 oxide of iron. Consequently, 76,800 grains (10 lbs. 

 hessian) of blood contain 61*54 grains of peroxide 

 of iron in arterial blood, = 55*14 of protoxide in 

 venous blood. 



Let us now assume that the iron of the globules 

 of venous blood is in the state of protoxide. It 

 follows, that 55*14 grains of protoxide of iron, in 

 passing through the lungs, take up, in one minute, 

 6*40 grains of oxygen (the quantity necessary to 

 convert it into peroxide). But since, in the same 

 time, the 10 lbs. of blood have taken up 12 grains 

 of oxygen, there remain 5*60 grains of oxygen, 

 which combine with the other constituents of the 

 blood. 



Now, 55*14 grains of protoxide of iron combine 

 with 34*8 grains of carbonic acid, which occupy the 

 volume of 73 cubic inches. It is obvious, therefore, 

 that the amount of iron present in the blood, if in 

 the state of protoxide, is sufficient to furnish the 

 means of carrying or transporting twice as much 

 carbonic acid as can possibly be formed by the 

 oxygen absorbed in the lungs. 



The hypothesis just developed rests on well-known 

 observations, and, indeed, explains completely the 



T 



