116 THE VITAMINS 



grams were used, three for each of the yeasts. The birds were kept in 

 individual cages and were forcibly fed 20 grams of ground white rice, 

 18 cubic centimeters of distilled water, and the yeast, the experiment 

 being continued for at least 63 days. 



Extremely variable results were obtained with the different yeasts 

 in the pigeon tests but fairly concordant ones in the rat tests. This was 

 also true with the Osborne-Wakeman fraction II of the various yeasts. 

 Moreover, although the concentration of the protective factor was 

 higher in one of the samples of bakers' yeast than in the brewers' yeast, 

 the condition was reversed in the respective fractions. It was doubtless 

 the irregularity of results in the pigeon tests that led Levene to use 

 the rat in his later attempts to determine the chemical nature of vitamin 

 B as noted previously. 



Hauge and Carrick (1926) criticized these studies of Emmett and 

 Luros and of Levene and Muhlfeld in that the diets for the pigeons 

 were deficient in substances other than water-soluble vitamins and that 

 different species and different stages of life were involved in testing 

 for the two factors. To avoid both of these sources of error, they 

 used baby chicks as their experimental animals for testing both factors. 

 Preliminary experiments had shown that with dried brewers' yeast as 

 the sole source of vitamin B, young chicks grew very rapidly but de- 

 veloped polyneuritis in a short time ; while with corn as the sole source 

 of the vitamin, polyneuritis was prevented but growth was very slow. 

 This suggested the probability that the corn was rich in the antineuritic 

 factor but relatively poor in a growth-promoting factor, while the 

 opposite was true of the yeast. To test this further, corn and yeast 

 were fed at different levels, separately and combined, in rations other- 

 wise identical and furnishing adequate protein, salts and fat-soluble 

 vitamins. With 30 per cent of corn as the sole source of vitamin B, 

 the chicks grew slowly and showed no symptoms of polyneuritis during 

 the 18 weeks of the test ; whereas, when the corn was replaced by 

 yeast, the chicks grew rapidly but developed polyneuritis during the 

 tenth week and died within two weeks thereafter. With 20 per cent 

 of corn and 10 per cent of yeast, growth was rapid and only a few 

 cases of polyneuritis developed. With lower levels of corn and yeast, 

 some polyneuritis developed in all of the lots. Growth was rapid on 

 as small an amount as 10 per cent of yeast and slow even with large 

 amounts of corn. 



In discussing these results Hauge and Carrick emphasized the non- 

 identity of the antineuritic vitamin and the so-called water-soluble, 

 growth-promoting vitamin and the simultaneous occurrence of the two 



