VITAMIN G {B.) 115 



while at higher temperatures the antineuritic vitamin seemed to be 

 less stable to heat and alkali than the rat growth-promoting vitamin. 



Comparable results were obtained in a series of experiments in 

 which the same source of water-soluble vitamins, unmilled rice, was 

 used for studies on polyneuritis in pigeons, and on the rate of growth 

 in young rats. In the case of pigeons, the unmilled unground rice con- 

 stituted the sole food while with rats it was supplemented with lactal- 

 bumin, salt mixture, butterfat and lard to form a balanced ration for 

 growth. The results obtained in feeding experiments in which the rice 

 had been subjected to different heat treatments showed that "while 

 the antineuritic vitamin is stable to heat at 120° C. and 15 pounds 

 pressure for 1 hour, partially altered by heating in the air oven at 

 120° C. for 2 hours and totally destroyed at 120° C. and 15 pounds 

 pressure in 2 and 3 hours, the water-soluble B vitamin (rats) appears 

 to be stable to heat at these same temperatures, that is, it is not distinctly 

 or totally broken down. 



"These findings suggest, tentatively, at least, that the antineuritic 

 (pigeons) and the water-soluble B (rats) vitamins are not the same, 

 and that it would be better to consider them as being different until 

 there is further proof to the contrary." The question could not then 

 be definitely settled because of lack of quantitative methods and of 

 accurate knowledge of the nutritional requirements of the experimental 

 animals. 



Funk and Dubin (1921) reported a separation by fractional ad- 

 sorption of autolyzed yeast with norite of two vitamins of the B type, 

 both of which fractions appeared to be needed by rats. On either alone, 

 rats grew only for a few weeks at a slow rate, and after two months 

 death ensued. Increasing the amount of either did not have any effect; 

 feeding both produced rats normal in regard to growth and appearance. 

 These findings were so briefly reported that they did not influence 

 greatly the thinking on the subject. 



Further evidence of the nonidentity of the two vitamins (or the 

 interference of unknown factors) was furnished by Levene and Muhl- 

 feld (1923) in a comparison of the behavior of three samples of bakers' 

 and one of brewers' yeast in protective experiments with pigeons and 

 growth experiments with young rats. The basal diet for the rats con- 

 sisted of casein 18, salt mixture 4, starch 54, butterfat 9, lard 13, and 

 cod-liver oil 2 parts. Young rats were placed in individual cages and 

 fed this diet until they had definitely lost in weight, when the yeast was 

 given in tablet form. Four or more animals were used for each sample 

 of yeast tested. For the pigeon experiments, birds weighing over 300 



