118 THE VITAMINS 



B. This demonstration that yeast contains a heat-stable factor essential 

 for growth was confirmed by a further series of feeding experiments 

 in which it was shown that young rats failed to grow on a diet of 

 purified casein 18, salt mixture 4, 2 per cent Seidell vitamin B picrate 

 in milk sugar 1, cod-liver oil 2, olive oil 8, and starch 67 parts, but 

 began to gain weight promptly upon the substitution of 5 per cent of 

 autoclaved yeast for an equivalent amount of starch. The same diet 

 including the autoclaved yeast but not the vitamin B picrate resulted 

 in a gradual loss in weight, followed by death within 3 or 4 weeks. 



In another series of experiments, rats which were declining in 

 weight on a vitamin-B-free diet were given graded amounts of a vita- 

 min B fraction, with 500 milligrams daily of autoclaved yeast. The 

 growth response to 2.5 and 5 milligrams daily of the vitamin B frac- 

 tion in combination with the autoclaved yeast was approximately the 

 same as that obtained with 200 and 500 milligrams, respectively, of 

 dried brewery yeast under the same experimental conditions. Since fair 

 growth resulted when the fraction was fed in doses of 15 milligrams 

 or more without being supplemented with autoclaved yeast, it was con- 

 cluded that some of the heat-stable factor was present in the yeast 

 fraction. 



Seidell (1926a) repeated the work of Smith and Hendrick with 

 rats and also tested the supplementary effect of autoclaved yeast for 

 one of his antineuritic concentrates in pigeon experiments. When young 

 rats were fed a diet in which the antineuritic vitamin concentrate served 

 as the sole source of vitamin B, there was no growth response until 

 the autoclaved yeast was added, when there was a rapid response as 

 had been noted by Smith and Hendrick. On the other hand, pigeons on 

 a diet of polished rice supplemented by just enough of the vitamin 

 concentrate to keep them at constant weight showed no growth response 

 following the addition of autoclaved yeast. On the assumption that 

 vitamin B is composed of the antineuritic vitamin and another con- 

 stituent, in itself active or inactive as regards growth, Seidell sug- 

 gested the possibility that the rat (and probably other mammals) needs 

 both of these constituents and the pigeon only the antineuritic vitamin. 

 (Cf. WilHams and Waterman, 1927-8.) 



The paper of Smith and Hendrick was followed closely by one 

 from Goldberger, Wheeler, Lillie, and Rogers (1926) in which it was 

 suggested that the heat-stable substance in yeast is concerned with the 

 prevention and cure of pellagra. A long-continued investigation of 

 the relation of diet to pellagra, begun in 1914 by Goldberger, Waring 

 and Willets of the U. S. Public Health Service, had led to the announce- 



