162 
PHYSIOLOGY: OSBORNE AND MENDEL Proc. N. A. S. 
In view of the success of the foregoing experiments we have investi- 
gated the possibility of nourishing animals on food mixtures from which 
both carbohydrates and fats have been eliminated as far as possible. 
The attempts have thus far resolved themselves essentially into feeding 
a diet of which more than 90 per cent consists of protein, along with 5 
per cent of inorganic salts and vitamins in the form of small daily doses 
of dried alfalfa and brewery yeast. 
Although it has been demonstrated by experiments of Pfliiger 7 that a 
carnivorous animal can be kept alive and maintained in activity of 
considerable periods on an exclusive diet of meat, it has been stated that 
omnivora and herbivora cannot survive on such a ration. In our own 
trials 8 in which the vitamin-bearing substances, representing 4-8 per 
cent of the food eaten, were the only noteworthy sources of either fat or 
carbohydrate, a number of animals have already approximately tripled 
their size, growing at essentially a normal rate for their species. 
In all of the experiments on the unusual diets reported in this communi- 
cation the protein content of the food mixtures was unusually high. Ac- 
cordingly the question may well be raised whether a comparatively high 
protein content in the dietary during growth is not actually advantageous 
rather than detrimental as has been suggested by certain writers. Whether 
animals will attain full adult size and normal function on diets furnishing 
protein as the almost exclusive source of energy and tissue substance 
cannot be foretold at the present time. In any event the experience 
gained from these newest studies raises a number of important problems 
of physiological interest and also suggests new possibilities of investi- 
gation from novel standpoints. 
* The expenses of this investigation were shared by the Connecticut Agricultural 
Experiment Station and the Carnegie Institution of Washington, D. C. 
iMagendie, F.,Ann. Chim. Phys., 3, 1816 (66). 
* Osborne, T. B., and Mendel, L. B., Biol. Chem., 45, 1920 (145). 
3 Drummond, J. C, Proc. Physiol. Soc, J.Physiol., 54, 1920 (xxx). 
4 Maignon, F., Recherches sur le role des graisses dans V utilisation des albumnoides. 
Lyon, 1919. 
5 Osborne, T. B., and Mendel, L. B., Proc. Soc. Exper. Biol. Med., 18, 1921 (136). 
6 Lusk, G., The Science of Nutrition. Philadelphia, 1917, p. 288. 
7 Pfliiger, K., Pfluger's Arch., 50, 1891 (98); 77, 1899 (425). 
8 A preliminary account of this is given by Osborne, T. B., and Mendel, L. B., 
Proc. Soc. Exper. Biol. Med., 18, 1921 (167). 
