EXHALED FROM THE LUNGS. 113 



^th be deducted as oxygen, there will still remain 108 

 cubic inches of nitrogen, which occupy the space of 

 3 Ibs. of water. Now, whatever may be the actual 

 amount of the nitrogen thus swallowed, it is certain that 

 the whole of it is given out again by the mouth, nose, 

 and skin ; and when we consider the very large quanti- 

 ty of nitrogen found in the intestines of executed crim- 

 inals by Magendie, as well as the entire absence ot 

 oxygen in these organs (26), we must assume that air, 

 and consequently nitrogen, enters the stomach by re- 

 sorption through the skin, and is afterwards exhaled by 

 the lungs. 



When animals are made to respire in gases contain- 

 ing no nitrogen, more of that gas is exhaled, because in 

 this case the nitrogen within the body acts towards the 

 external space as if the latter were a vacuum. (See 

 Graham, " On the Diffusion of Gases.") 



The differences in the amount of expired nitrogen in 

 different classes of animals are thus easily explained ; 

 the herbivora swallow with the saliva more air than the 

 carnivora ; they expire more nitrogen than the latter, 

 less when fasting than immediately after taking food. 



13. In the same way as muscular fibre, when sep- 

 arated from the body, communicates the state of de- 

 composition existing in its elements to the peroxide of 

 nydrogen, so a certain product, arising by means of the 

 vital process, and in consequence of the transposition 

 of the elements of parts of the stomach and of the 

 other digestive organs, while its own metamorphosis is 

 10* 



