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57 
another more in harmony with the modern teachings of physio- 
logical chemistry, and we divide the primordial elements of food in two 
great classes, namely, the organic and inorganic principles. In the 
latter class enter the salts and water, and the organic compounds are 
considered under two divisions : nitrogenous and non-nitrogenous. 
It is to the groups of organic substances that belong the albumin- 
oids, the chief flesh formers of our body. Still, in spite of their great 
nutritive value, these albuminoids, taken separately cannot alone sustain 
animal life and in order that they should acquire a real nutritive value, 
it is necessary that they must be associated, not only to the other sub- 
stances of other classes of food, but even to the different kinds of 
albuminoids themselves. For instance, an animal fed on albumen or 
on gelatine alone, would very soon succumb, as it has been demon- 
strated by Papin, Magendie and Hammond's experiments. 
Now, gentlemen, the food which contains the greatest quantity of 
nutritious substances is not always the one that is digested the most 
easily ; on the contrary, we shall see that certain very nutritious aliments 
are of a slow and painful digestion. We must acknowledge, besides 
that several causes bring modification to the precise rules that we might 
establish with regard to the digestibility of food ; it would be difficult 
nowadays to classify alimentary substances into light and heavy aliments. 
One of the chief objections to this classification would be individual 
predisposition. In fact many would easily digest foods which would 
infallibly produce indigestion in others. 
We must add to this : Habit, which permits the digestive tube to 
get accustomed to such and such aliment. 
But there is a point upon which physicians and physiologists agree ; 
it is the importance of the state of cohesion, and the looser is that 
cohesion the easier is the digestion. There exists, in the same sub- 
stance, very wide differences, according to the different states in which 
that substance is presented, and nothing is more interesting than the 
results given by Schiff upon the digestibility of a given quantity of 
albumen taken in solid and compact mass or else administered finely 
divided. 
Digestive value and nutritive value of food, are therefore two 
different things and we could say with Trousseau : " That the most 
