VITAMIN G (B.) 117 



factors in varying proportions in different food materials, as shown 

 by the supplementing action of one material for another in meeting 

 the combined nutritional need of the prevention of polyneuritis and 

 the promotion of growth. 



That vitamin B as the term was then used might be a composite of 

 two or more factors occurring in varying proportions in different ma- 

 terials had been suggested incidentally by McCollum, Simmonds and 

 Becker (1925) in an attempt to explain the apparent inferiority of 

 yeast as contrasted with wheat germ (as the sole source of vitamin 

 B) in protecting rats against faulty salt mixtures. Suggesting as an 

 explanation that vitamin B is more than one substance, they said, "It 

 may be possible that yeast contains both of these principles but in 

 different proportions than are contained in wheat germ, and that on 

 this basis one may explain the inferiority of yeast as contrasted with 

 germ in protecting the rats against our faulty salt mixtures. For ex- 

 ample, one might speculate that there are two nutritive essentials com- 

 posing vitamin B, which may be designated as y and s. In yeast, y 

 may be present in lesser amount than s, and so when the minimum 

 amount of yeast is fed which can support growth in the rat when the 

 rest of the diet is well constituted, y is the limiting factor, and 2 is 

 fed more liberally than y. In wheat germ y and 2 might be present in 

 more favorable proportions (in certain samples) than in yeast, so that 

 when fed to the amount of 4 per cent of the diet, likewise well con- 

 stituted, neither y nor 2 would be provided in minimal amount, hence 

 the physiological stability would be greater in this case than when 

 the minimum amount of yeast is fed. When the diet is appropriately 

 constituted, little or no difference might be demonstrable between the 

 values of yeast and germ as sources of vitamin B (y and s), but the 

 superiority of one over the other might be demonstrable when the 

 diet is made unfavorable through the addition of inappropriate salt 

 mixtures." 



In the course of an investigation of the influence of dietary de- 

 ficiencies on experimental tuberculosis in the albino rat, Smith (1926) 

 found that a diet containing 40 per cent of rolled oats (considered to 

 be rich in vitamin B), together with an adequate amount of casein, 

 salts, and vitamin A, failed to promote normal growth in young rats. 

 An attempt to determine the nature of the deficiency in this diet led 

 to the important discovery (Smith and Hendrick, 1926) that the diet 

 could be made adequate for growth by the addition of 5 or 6 per cent 

 of dried brewery yeast even after the yeast had been autoclaved for 

 6 hours at 15 pounds pressure, a procedure believed to destroy vitamin 



