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field for study among the carbohydrates appears very fruitful, 
and it may be that large differences in the nutritive effects of 
these various sugars, starches, and other carbohydrates will de- 
velop when thorough exploration is made. That physiological 
research already indicates these differences is manifest in a paper 
by Mendel and Mitchell.^® That the unmistakable appetite of 
pigs for “milk’’ whey, skim-milk, and buttermilk may be in part 
accounted for by the superior value of lactose, the sugar of milk, 
is not beyond the pale of reasonable expectation. 
"Why is cane-sugar, in its absence, but in the presence of an 
abundance of starches in general, so much craved by small grow- 
ing children, and by men fatigued? 
The problem of “balancing the diet or ration”, respectively 
of men and other animals on the basis of known physiological 
and chemical knowledge deepens as the intricate and involved 
elements of nutrition are carefully scrutinized. 
The fats, heretofore thought to be interchangeable, are now 
commanding considerable attention because of their specific ef- 
fects. It is demonstrated that there is a marked difference in 
the ordinary fats such as butter-fat, cod-liver oil, beef fat and 
oils, cottonseed oil, olive oil, com oil, and so on. 
McCollum and Davis^® have shown with rats that nutritive 
failure “sooner or later supervenes” when they have been 
brought through a period of successful growth on diets of puri- 
fied food constituents, but containing no flats. 
Now Osborne and MendeP®, practically simultaneously, were 
carrying on similar rational research with these “high carbon 
and hydrogen with low oxygen” (compared to proteins and 
starches) compounds, demonstrating likewise that the fats, or 
some unknowns associated with them, possess peculiar but abso- 
lutely essential nutritive properties. 
Strikingly enough, McCollum and Davis secured positive favor- 
able nutritive results with ‘ ‘ butter-fat, egg yolk fats, kidney fat 
(ether soluble portion of kidney free from visible fat), and the 
isMendel, Lafayette B., and Mitchell, P. H. ; Chemical Studies on Growth, 
Am. Jour. Physiol., 1907, XX, 81. See also Mendel, Lafayette B. : Nutrition 
and Growth (Note 15), pp. 1539-1547 for discussion of carbohydrate nu- 
trition. 
i^McCollum, E. V. and Davis, Marguerite: Jour. Biol. Chem., 1913, XV, 
p. 167 ; 1914, XIX, p. 245 ; 1915, XX, 641 ; and 1915, XXI, 179. 
20Osborne, Thomas B., and Mendel, Lafayette B. : Jour. Biol. Chem., 1912, 
XII, 81 ; The Relation of Growth to the Chemical Constituents of the Diet, 
Jour. Biol. Chem., 1913, XV, 311 ; The Influence of Butter-Fat on Growth, 
Jour. Biol. Chem., 1913, XVI, 423 ; The Influence of Cod-Liver Oil and some 
Other Fats on Growth, Jour. Biol. Chem., 1914, XVII, 401 ; see also Proc. 
Soc- Exper. Biol, and Med., 1915, XII, 92. 
