570 INDUCTION. 



The mysterious chemical phenomena connected 

 with respiration can now, by a beautiful deductive 

 process, be completely explained. The arterial blood, 

 containing iron in the form of hydrated peroxide, 

 passes into the capillaries, where it meets with the 

 decaying tissues, receiving also in its course certain 

 non-azotised but highly carbonised animal products, 

 in particular the bile. In these it finds the precise 

 conditions required for decomposing the peroxide into 

 oxygen and the protoxide. The oxygen combines 

 with the carbon of the decaying tissues, and forms 

 carbonic acid, which, although insufficient in amount 

 to neutralize the whole of the protoxide, combines 

 with a portion (one-fourth) of it, and returns in the 

 form of a carbonate, along with the other three- 

 fourths of the protoxide, through the venous system 

 into the lungs. There it again meets with oxygen and 

 water: the free protoxide becomes hydrated peroxide; 

 the carbonate of protoxide parts with its carbonic acid, 

 and by absorbing oxygen and water, enters also into 

 the state of hydrated peroxide. The heat evolved in 

 the transition from protoxide to peroxide, as well as 

 in the previous oxidation of the carbon contained 

 in the tissues, is considered by Liebig as the cause 

 which sustains the temperature of the body. But 

 into this portion of the speculation we need not 

 enter*. 



* As corroborating the opinion of Liebig that the protoxide of 

 iron in the venous blood is only partially carbonated, the fact has 

 been suggested, that the system shows great readiness to absorb an 

 extra quantity of carbonic acid, as furnished in effervescing drinks. 

 In such cases the acid must combine with something, and that 

 something is probably the free protoxide. It would be worth 

 ascertaining whether the protoxide itself or its carbonate has the - 

 greater facility in absorbing oxygen and turning itself into hydrated 



