204 THE VITAMINES 



pigeons and on the other, together with lactalbumin, butter, salts and 

 lard, to rats. Vitamine B, which is necessary for pigeons, appeared to 

 be unstable and was totally destroyed by heating for 2 hours at 

 1 20C . , while rats could still grow on the above food mixture . Emmett 

 and Luros came to the conclusion that these vitamines are different 

 from each other. Nevertheless, we saw in our investigations on 

 yeast, contrary to the above experiment, that vitamine B was resis- 

 tant to heat; furthermore, in the experiments of these workers one kind 

 of animal was fed rice alone while the other received various addi- 

 tions. As we shall see later, protein may easily take the place of a 

 vitamine addition, besides which, these animals may differ with 

 respect to their vitamine requirements. 



As regards the identity of the growth substance for yeast with 

 vitamine B, the question is of particular importance since we must 

 know, when using the yeast method described in the previous chapter, 

 which substance we are determining. There is no doubt, however, 

 that the substance important for the growth of yeast is much more 

 stable to heat, and yet we saw in the chapter on the chemistiy of 

 vitamines, that vitamine B resists many manipulations, and still 

 retains its activity after many weeks of work. Emmett and Stock- 

 holm (531), on the contrary, saw that strongly heated unpolished 

 rice, although inactive for pigeons, is just as active as the natural 

 product for yeast cells. The same findings were obtained with fil- 

 trates resulting from the treatment of extracts with fuller's earth. 

 In these cases, the filtrates were active for yeast but not for rats. 6 

 Emmett and Stockholm believed that further research must establish 

 either the identity or dissimilarity of these substances, and it would 

 not be correct in the meanwhile, to regard the yeast method as 

 suitable for the determination of vitamine B. 



Recently, Funk and Dubin (I.e. 129d) have corroborated the 

 statement of Emmett and Luros that the yeast substance is not 

 identical with vitamine B. If autolyzed yeast is shaken with a 

 small amount of fuller's earth vitamine B is usually removed almost 

 quantitatively. Now if the filtrate from the above is repeatedly 

 shaken with larger amounts of fuller's earth, the substance acting 



'Karr (I.e. 404), working on dogs, noted that vitamine B of yeast is very 

 stable. Autoclaving for 3 to 4 hours with subsequent heating at 108C. for 

 72 hours destroyed only a part of this substance. 



