CHAPTER III. 



ALIMENTARY ENERGETICS. 



Various Problems of Alimentation. § i. Food the source of 

 Energy and Matter. The two forms of Energy afforded by 

 Food — Vital Energy, Thermal Energy. Food the source 

 of Heat. The role of Heat. — § 2. Measure of the output of 

 Energy— hy the Calometric Method— by the Chemical 

 Method. — § 3, The regular type of Food, Biothermogenic, 

 and the irregular type, Thermogenic. — § 4. Food considered 

 as the source of Heat. The Law of Surfaces. The limits 

 of Isodynamics.— § 5, Plastic role of Food. Preponderance 

 of Nitrogenous Foods, 



Among the problems on which energetics has 

 thrown a vivid h'ght we have mentioned alimentation, 

 muscular contraction, and, more general still, the 

 intermittence of vital functional activity. We shall 

 begin with the study of alimentation. 



The Different Problems of Alimentation. — What is a 

 food? In what does alimentation consist? The 

 dictionary of the Academic will give us our first 

 answer. It tells us that the word food is applied to 

 "every kind of matter, whatever may be its nature, 

 which habitually serves or may serve for nutrition." 

 This is very well put, but here again we must know 

 what nutrition is, and that is not a simple matter; in 

 fact, it practically means whatever is usually placed 

 on the table in a civilized and polished society. But 



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