Existence of a Hitherto Unknown Dietary Factor Essential for Reproduction

If female rats are reared on the now well known "synthetic" nutritive regimen consisting of fat, carbohydrate and protein in relatively pure, separate form, to which are added an appropriate salt mixture and daily doses of the vitamins A and B, normal growth and every appearance of health results. The animals are of splendid size, sleek coated and active. Depending somewhat on the season of the year, either a large proportion or, indeed, practically all of such animals are sterile. We have employed a basic ration of casein (18), cornstarch (54) and lard (15), following Osborne and Mendel, to which milk fat (9) and salts 1 (4) are added, the animals receiving separately and daily from 0.4 to 0.6 gm. of dried whole yeast (Harris). The sterility produced is a dietary deficiency disease, and can be quickly cured by a change of dietary regimen. It yields a highly characteristic picture,