Feeding experiments illustrating the importance of accessory factors in normal dietaries

THE experiments described in this paper confirm the work of others in showing that animals cannot grow when fed upon so-called " synthetic " dietaries consisting of mixtures of pure proteins, fats, carbohydrates, and salts. But they show further that a substance or substances present in normal foodstuffs (e.g. milk) can, when added to the dietary in astonishingly small amount, secure the utilization for growth of the protein and energy contained in such artificial mixtures. The particular experiments, of which an account is now to be given, were undertaken to put upon a more quantitative basis results which I obtained as far back as 1906-1907 1. Since that time, a fuller realization of the fact that (leaving on one side the influence of the inorganic constituents of dietaries) protein supply and energy supply do not alone secure normal nutrition, has ariseni from the extremely interesting recent work upon the etiology of such diseases as beri-beri and scurvy2. It is not surprising that much work is now beingf done in connection with the subject; and since the experimental results given in this paper were obtained, the publications of others have covered part of the ground. In particular I may refer to the work of Stepp" upon mice, and to the extensive researches of Osborne and Mendel4 upon rats. But the observations now to be described differ in some important details from those of the authors quoted. They bring out in