310 DR ALISON'S OBSERVATIONS ON 



carbon and hydrogen, as that Avhich exists in the blood, or in the textures of ani- 

 mals. As there is, in the whole of the ingesta of animals, a great excess of car- 

 bon and hydrogen over their proportion to azote in albumen, and as oxygen is 

 always present in the blood, it is quite possible that a part of the azote of the 

 albumen taken in, may be thrown off in combination with portions of those other 

 elements, by the bowels and kidneys, without entering into the textures ; and 

 that the nourishment of the textures may be in part due to fresh albumen, formed 

 in the animal bodj'^ by help of oxygen from the lungs, and of azote taken in by 

 another channel ; just as we are nearly sure that part of the oil taken into an 

 animal is often decomposed and thrown off, and that fresh fat is often formed 

 from the starch or sugar of the ingesta. 



There is one mode, pointed out by Liebig, in which we can have no doubt 

 that azote must be introduced into the blood of animals, independently of the al- 

 buminous ingesta, viz., by the air which is contained in the water, and still more 

 in the saliva, continually taken into the stomach. " During the mastication of 

 the food, there is secreted into the mouth, from organs specially destined to this 

 function, a fluid, the saliva, which possesses the remarkable property of inclosing 

 air in the shape of froth, in a far higher degree than even soap-suds. This air, by 

 means of the saliva, reaches the stomach with the food, and there its oxygen en- 

 ters into combination, while its nitrogen is given out through the skin and lungs."* 



Now, what proof is there that the azote, thus believed to be set free in the 

 stomach, is excreted, unchanged, by the skin and lungs ? Is it not much more 

 probable that it enters into fresh combinations in the primee vife and in the blood, 

 and is only separated from the blood, when, by the agency of the oxygen of the 

 air, acting, under the circumstances to be afterwards stated, with peculiar energy 

 on some of the constituents of the blood, it is disjoined from its union with carbon 

 and hydrogen. 



In fact, the azote thus set at liberty in the stomach, must be in circumstances 

 almost exactly similar to those in which, according to the statements of Mulder 

 and others, ammonia is formed from air, even by the help of inorganic matter ; still 

 more when organic matter, although non-azotised, is present in a state of decom- 

 position, or an analogous condition.! " By all porous substances ammonia is pro- 

 duced, — provided they are moist, are filled with atmospheric air, and are exposed 

 to a certain temperature." 



" When reddened litmus paper is hung up in a bottle, filled with pure atmo- 

 spheric air, and when pure iron-filings, moistened with pure water, are laid at the 

 bottom, then the red litmus is quickly turned blue by the action of ammonia, 

 formed from the nitrogen on the air, and the hydrogen of the decomposed water, 

 the oxygen of which had combined with the iron. 



* Liebig's Animal Chemistry, pp. 113-4. 

 f Mulder, p. 149, et seq. 



