NUTRITION. 47 



other nitrogenized compounds, occurring in plants, are 

 either rejected by animals, as in the case of the charac- 

 teristic principles of poisonous and medicinal plants, or 

 else they occur in the food in such very small propor- 

 tion, that they cannot possibly contribute to the increase 

 of mass in the animal body. 



The chemical analysis of these three substances has 

 led to the very interesting result that they contain the 

 same organic elements, united in the same proportion by 

 weight ; and, what is still more remarkable, that they 

 are identical in composition with the chief constituents 

 of blood, animal fibrine, and albumen. They all three 

 dissolve in concentrated muriatic acid with the same 

 deep purple color, and even in their physical characters, 

 animal fibrine and albumen are in no respect different 

 from vegetable fibrine and albumen. It is especially to 

 be noticed, that, by the phrase, identity of composition, 

 we do not here imply mere similarity, but that even in 

 regard to the presence and relative amount of sulphur, 

 phosphorus, and phosphate of lime, no difference can 

 be observed, (s) 



How beautifully and admirably simple, with the aid 

 of these discoveries, appears the process of nutrition in 

 animals, the formation of their organs, in which vitality 

 chiefly resides ! Those vegetable principles, which in 

 animals are used to form blood, contain the chief con- 

 stituents of blood, fibrine, and albumen, ready formed, 

 as far as regards their composition. All plants, besides, 

 contain a certain quantity of iron, which reappears in 

 the coloring matter of the blood. Vegetable fibrine and 



