THE DOCTRINE OF VITAL UNITY. I53 



which it takes place. It is, in fact, a chemical 

 transformation of an alimentary substance. This 

 transformation may be realized outside the organism, 

 in vitro, just as it can in the living being without 

 masticating organs, without an intestinal apparatus, 

 without glands, in a vessel placed in a stove, simply 

 by means of a few soluble ferments — pepsine, trypsine, 

 amylolytic diastases. 



All alimentary substances, whether taken from 

 without or borrowed from the reserves accumulated 

 in the internal stores of the organism, must undergo 

 preparation. This preparation is digestion. Diges- 

 tion is the prologue of nutrition. It is over when the 

 reparative substance, whether food or reserve-stuff, 

 is brought into a state enabling it to pass into the 

 blood, and to be utilized by the organism. 



The Identity of Categories of Foods in the Tivo 

 Kingdoms. — Now the alimentary substances are the 

 same in the two kingdoms, and so is their digestive 

 preparation. Alimentary materials are of four 

 kinds : albuminoid, starchy, fatty, and sugary sub- 

 stances. The animal takes them from without 

 (food properly so-called), or from within (reserve- 

 stuff). Man obtains starch, for instance, from different 

 farinaceous dishes. It may, however, equally well 

 be borrowed from the reserve of flour that we carry 

 within us in our liver, which is a veritable granary, 

 full of floury substance, glycogen. And so it is with 

 vegetables. The potato has its store of flour in its 

 tuber just as the animal has in its liver. The grain 

 which is about to germinate has it in reserve-stuff in 

 its cotyledons, or in its albumen. The bud which is 

 about to develop into a tree or a flower carries it at 

 its base. 



