98 BOARD OF AGRICULTURE. 



//, Non-Nitrogenous Constituents of Food. 



(As starch, sugars, organic acids, cellular substance, dextrine, gums, 



fats, etc.) 



The composition and the general character of some of the 

 principal non-nitrogenous organic plant constituents, and 

 their relation to the animal economy, engaged Liebig's atten- 

 tion not less than that of the nitrogenous substances. 



Many organic substances, which did not contain nitrogen, 

 had already been studied with more or less success by other 

 chemists, before Lielng turned his scientific eiforts towards 

 the application of chemistry in the study of animal physi- 

 ology. 



The elementary composition of the starch, the sugars, the 

 fats, the principal organic acids, cellular substances, etc., 

 was known; all consisted of but three elements — carbon, 

 hydrogen, oxygen. 



The fats of plants and of animals had been carefully stud- 

 ied by Cheuvoreal and others ; it had been proved that they 

 are composed of the same constituents, and that they are in 

 every way identical. The changes of the starch and the veg- 

 etable cellular mass into sugar by the aid of mineral acids, 

 and of the sugar into carbonic acid and alcohol by means 

 of some nitrogenous organic matter, had been described. 

 Liebio-'s main eftbrts in this connection were directed towards 

 the study of the origin and the functions of the fat in the 

 animal system. 



But little attention had been thus far paid to the solution 

 of these questions. 



The animal fat was still considered a kind of stored up 

 food, which in time of need would support life in conse- 

 quence of an assumed disposition to combine with the nitro- 

 gen of the air, forming thereby nitrogen containing animal 

 matter, like blood and flesh. Liebig, for ol)vious reasons, 

 discarded these opinions. His own experience induced him 

 to teach, as far as the origin of the fat in the animal system 

 was concerned, that quite frequently a large proportion of 

 the animal fat was produced in the animal, and not merely 

 derived from the vegetable food it had consumed. He did 

 not deny that the fat contained in the latter was absorbed 



