ALBUMEN, AND CASEINE. 47 



This is vegetable albumen. It is found in the great- 

 est abundance in certain seeds, in nuts, almonds, 

 and others, in which the starch of the graminese is 

 replaced by oil. 



The third nitrogenised constituent of the vegeta- 

 ble food of animals is vegetable caseine. It is chiefly 

 found in the seeds of pease, beans, lentils, and 

 similar leguminous seeds. Like vegetable albumen, 

 it is soluble in water, but differs from it in this, that 

 its solution is not coagulated by heat. When the 

 solution is heated or evaporated, a skin forms on its 

 surface, and the addition of an acid causes a coagu- 

 lum, just as in animal milk. 



These three nitrogenised compounds, vegetable 

 fibrine, albumen, and caseine, are the true nitro- 

 genised constituents of the food of graminivorous 

 animals ; all other nitrogenised compounds, occur- 

 ring in plants, are either rejected by animals, as in 

 the case of the characteristic i3rincij)les of poisonous 

 and medicinal plants, or else they occur in the food 

 in such very small proportion, 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 con- 

 tain the same organic elements, united in the same 

 proportion by weight ; and, what is still more re- 

 markable, that they are identical in composition 

 with the chief constituents of blood, animal fibrine, 

 and albumen. They all three dissolve in concen- 



