ALIMENTARY ENERGETICS. I43 



reality, food has many other offices to fulfil than 

 that of warming the body and of giving it energy — 

 that is to say, of providing for the functioual activity 

 of the living machine. It must also serve to provide 

 for wear and tear. The organism needs a suitable 

 quantity of certain fixed principles, organic and 

 mineral. These substances are evidently intended to 

 replace those which have been involved in the cycle 

 of matter, and to reconstitute the organic material. 

 To these materials we may give the name of histo- 

 genetic foods (repairing the tissues), or of plastic 

 foods. 



§ 5. The Plastic R6le of Food. 



Opinions of the Early PJiysiologists.-^\\. is from this 

 point of view that the ancients regarded the role of 

 alimentation. Hippocrates, Aristotle, and Galen 

 believed in the existence of a unique nutritive sub- 

 stance, existing in all the infinitely different bodies 

 that man and the animals utilize for their nourish- 

 ment. It was Lavoisier who first had the idea of a 

 dynamogenic or thermal role of foods. Finally, the 

 general view of these two species of attributes and 

 their marked distinction is due to J. Liebig, who 

 called them plastic and dynamogenic foods. In addition 

 he thought that the same substance should accumulate 

 the same attributes, and that this was the case with 

 the albuminoid foods, which were at once plastic and 

 dynamogenic. 



Preponderance of Nitrogenous Foods. — Magendie, in 

 1836, was the pioneer who introduced in this inter- 

 minable list of foods the first simple division. He 

 divided them into proteid substances, still called 



