618 FUNCTIONS OF ANIMALS. 



acid. Liebig conceives that it is the iron in the globules which 

 combines with the oxygen. It thus becomes peroxide. In the 

 capillaries the half atom of oxygen with which it had united 

 unites with carbon, and is converted into carbonic acid. This 

 carbonic acid combines with the protoxide of iron. In the lungs 

 the carbonic acid is displaced by the oxygen of the atmosphere, 

 and passes into the air, while an equal volume of oxygen gas 

 unites with the protoxide, and converts it into red oxide. This 

 explanation is certainly very ingenious. 



6. The air when emitted from the lungs has probably the 

 temperature of that organ, or is heated to about 98. It is load- 

 ed with moisture at that temperature. Now the force of the 

 vapour of water at 98 is 1 74 inch. Hence it follows that the 

 air expired from the lungs contains rather more than -^th o f its 

 volume of vapour, or every 100 cubic inches of air expired will 

 contain 5*9 cubic inches of vapour. But the specific gravity of 

 vapour at 98 is 0-0362, that of air being 1. This is nearly 2 ^th 

 part of the weight of the same volume of air. Hence the weight 

 of the aqueous vapour in every 100 cubic inches of air expired 

 is about 1*8 grain. This in 24 hours will amount to 4334 grains, 

 or somewhat more than 9 avoirdupois ounces. Such is the 

 quantity of moisture given out daily from the lungs of an adult 

 person. 



MM. Henri and Chevalier collected a quantity of the matter 

 of expiration of cows which had condensed on the ventilators of 

 a cow-house in Paris. It was a colourless liquid having an am- 

 rnoniacal smell. It contained no salt of lime, potash or soda, 

 but only salts of ammonia. These salts were, 

 Lactate ^ 



Carbonate /. 



. > of ammonia, 



Acetate 



Hippurate 



Also a balsamic volatile body from the dung of the cattle in the 

 stable. It is more than probable that the ammonia and the 

 acids combined owed their origin to the dung or urine of the 

 cattle rather than to what was expired from the lungs.* 



7. The opinion at present entertained respecting the effect of 

 respiration upon the azotic constituent of the air is not very de- 

 cided. Some suppose that the azote of the air is not affected by 



* Jour, de Pharm. xxv. 421. 

 4 



