TFIE INFLUENCE OF CHEMISTRY. 97 



nitrogenous constituents of various descriptions, and as a 

 rule in much larger proportions than generally conceded. 

 Seeds and young plants showed more than natural stems and 

 leaves. 



Liebig was the first scientist who pointed out the close 

 chemical relations which exist between the three principal 

 forms of nitrogenous constituents of plants and of animals ; 

 namely, albumen, filn-in and casein. 



He recognized, by careful analyses, an exceptionally large 

 accumulation of these substances in the seeds of many of our 

 prominent farm crops ; and found also that the blood, the 

 milk, the flesh, the nuiscles and the textm-e of animals 

 showed similar remarkable features in their composition. 

 He finally demonstrated, by actual experiment and otherwise, 

 that the vegetable organism, or the plant, alone was capa- 

 ble of producing from more elementary compounds, like car- 

 bonic acid, water, ammonia and some mineral constituents, 

 the complex nitrogen-containing proximate constituents of 

 plants and of animals. As he had proved, also, that the ani- 

 mal was incapable of producing in its own organism the mcsfc 

 characteristic constituents — as far as quantity and quality 

 w^ere concerned — of its own blood and flesh, etc., it became 

 evident that the healthful and normal condition of the ani- 

 mal, depended in a controlling degree, on the amount of cer- 

 tain nitrogenous substances contained in the vegetable food 

 consumed. The desirability of compounding the diet of the 

 animal, as far as the su[)ply of nitrogenous constituents is 

 concerned, with special reference to the particular wants of 

 its organization, as well as its conditions and its functions, 

 became not less apparent. I need scarcely to point out that 

 in the light of Liebig's teachings, the time-honored practice 

 of using the seeds of our cereals, some prominent leguminous 

 plants (clover, beans, pease, etc.), the brans and the oil- 

 cakes for enriching the fodder of farm stock finds for the first 

 time in the history of agriculture an intelligent explanation. 

 Liebig called the nitrooenous constituents of the animal food, 

 on account of their close relation to the formation of blood 

 and flesh, the plastic constituents of the food, and considered 

 them the source of animal energy, or interior and exterior 

 phenomena of motion. 



