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IOWA ACADEMY OP SCIENCE 
abundantly provided. On the contrary, that rule is fulfilled in 
the perfect development of the art of adapting food of any and 
every kind to the needs of the body according to the very varied 
circumstances, of the individual, at different ages, with different 
forms of activity, with different inherent personal peculiarities 
and with different environments”. Certainly Sir Henry would 
exhaust the possibilities in so far as source of food is concerned 
to gain or secure all of those simple and medium simple, and 
complex things that go to make up the body physiologic and to 
enable this living bundle of sinew, fibre, bone, nerve, and what 
not to work (live) to the fullest advantage. Most assuredly, 
the wider the variety the greater is the possibility of including 
in the diet or ration all of the essential nutrients ; when the 
appetite is completely followed there is ordinarily a wide range 
of choices made, and thus the liklihood of physiologic satisfaction 
is the greater. 
MendeP® has recently emphasized the great importance of 
the correct selection of efficient nutritive units, calling attention 
particularly to the fact that “we must know what nutrient units 
of any nature are indispensable, and further, whether a complete 
lack or deficit of them in the intake can be made good by direct 
synthesis”. The stupendous task of balancing the diet, or the ra- 
tion is clearly evident to students who scrutinize the evidence 
critically. 
In formulating dietaries for the feeding of humans as well as 
standards for animals in general there must be considered the 
great complexity of the ordinary food or feed constituents^ — ^pro- 
teins, carbohydrates, fats, and ash, of which, in addition to water, 
diets and rations are composed. Discussion concerning recent 
developments and newer viewpoints in nutrition, based upon a 
study of these food constituents is quite in place. That there 
are manifest differences and differences in the proteins, in the 
fats, in the carbohydrates, and in the ash of different foods is 
made clear in recent researches. 
Protein metabolism may be rightly studied and interpreted 
nowadays on the baels of the amino-acids present. Or as Men- 
deP^ puts it : “the protein requirement, we shall not err in iden- 
tifying it today with the specific amino-acid needs of the grow- 
^■‘Mendel. Lafayette U. : Nutrition and Growth, Jour. Am. Med. Ass’n., 
■1915, LXIV, pp. 1539-1547. 
