454 S. HENRY AYERS AND COURTLAND S. MXJDGE 



support growth of the streptococcus. The results shown in the 

 third section of table I indicate that the growth in such a medium 

 was just as good as the growth in our regular peptone medium 

 containing the extract of autolized yeast. 



We have only shown in our tables the result of growth in a 

 single flask, but these results have been duplicated many times 

 so that it is felt that the results presented express the general 

 average. 



The results of MacLeod and Wyon (1921) are interesting in 

 connection with our experiments. They conducted some experi- 

 ments on the growth of a streptococcus with extracts from various 

 substances. The used extracts from hver, kidnej^, egg yolk, 

 yeast, muscle, bran, and milk, and found that with the exception 

 of milk and bran the results seemed to favor the vitamine hy- 

 pothesis so far as small amounts were active. They found how- 

 ever, that yeast extract had but httle more growth promoting 

 power than muscle extract. In view of the high water-soluble 

 B content of yeast, and of its small amount or even absence in 

 muscle, these results appear to us again to indicate that the 

 water-soluble B is not the growth-promoting substance of yeast. 



MacLeod and Wyon also worked with the pneumococcus and 

 meningococcus and they point out that the growth-promoting 

 property of certain extracts did not bear a direct relation to the 

 known vitamine content, and that yeast had little or no effect 

 in promoting the growth of these organisms. 



A survey of the second and third experiments shows that an 

 attempt was made in two distinct ways to obtain data on the 

 relation of water-soluble B to the growth-promoting substance 

 or substances of yeast. In the second experiment accepted 

 methods were employed for removing a fraction from yeast 

 extract containing a large amount of water-soluble B. This 

 fraction with peptone did not support growth of the streptococcus 

 and this fact is very significant. In the third experiment ac- 

 cepted means were used for removing or at least greatly reducing 

 the water-soluble B content of the yeast extract. This extract 

 which should have been free or very nearh^ free from water- 

 soluble B, with peptone, supported growth of the streptococcus in 



