364 



Scientific Proceedings (123). 



Fleischmann's starch-free yeast air-dried by us did not pro- 

 duce normal growth when 0.2 gram of the dried yeast was fed 

 daily. Growth was not stimulated appreciably even when the 

 amount was increased to 0.6 gram daily although one female pro- 

 duced a litter of 3, two of which died soon after birth and the 

 remaining one of which never grew normally. Better results were 

 secured for a time in the case of other rats fed 0.2 gram daily 

 of dried starch-free yeast furnished us by the Fleischmann Yeast 

 Co. in the dried form but this growth was not maintained when 

 the yeast was increased to 0.4 gram daily. At the end of 16 

 weeks all these rats were undersized and no young were produced. 



Our results show clearly that yeast is a variable source of vita- 

 mine-B for growth and cannot be accepted as a standard product 

 in experiments in which a vitamine-B preparation is required. 

 Its efficacy depends upon the manner in which it is fed, the species 

 of yeast, and apparently also on the character of the wort in which 

 it is grown. Our results do not support the general belief that 

 yeast is an unusually rich source of vitamine-B for growth. 



Especially striking were the consistent failures of the rats fed 

 yeast as the sole source of vitamine-B to reproduce normally. 

 In fact, in most cases no reproduction was secured, although each 

 colony contained animals of both sexes. These results, especially, 

 have raised grave doubts in our minds as to the suitability of yeast 

 as a source of vitamine-B in nutrition experiments. 



