The Essential Nature of a New Growth Factor and Vitamin B6

THE availability of several of the vitamins in crystalline form has al-lowed the use of rather highly purified diets for rats (Oleson et al., 1939; Edgar et al.,, 1938; Lepkovsky et al., 1936). When chicks are placed on similar purified rations complete failure results. Variation in the nutritional requirements of chicks and rats has long been recognized. Thus in work with chicks it has been necessary to continue to use crude rations fortui-tously low in certain factors, or rendered so by proper treatment. However, a few simplified diets containing liver, fishmeal, bran, and other supplements, as the crude materials have been used by some workers with varying degrees of success. Graham et al. (1934) and Van der Hoorn et al. (1935) obtained good growth on a simplified diet containing 10 percent of wheat germ mid-1 Published with the approval of the Directo