Yeast as a Source of Vitamine B. 363 



in colonies on a basal diet of purified casein 18 per cent., salts 

 3.7 per cent., agar 2 per cent., butter fat 5 per cent., with dextrin 

 to make 100 per cent., and have supplied the vitamine-B in the 

 form of dried yeast of various sources, both as an integral part of 

 the diet or separately in the form of a tablet. Our results were as 

 follows: 



Air-dried Fleischmann's baker's yeast containing 40 per cent, 

 yeast in the dried product failed to produce normal growth in all 

 cases when the ration contained 4 per cent, or less of the dried 

 product, and certain individuals even failed to make normal 

 growth when the dried yeast formed 10 per cent, of the diet. 

 Out of 20 rats, 9 were females, and none of these produced young 

 during the 2 to 4 months of the experiment. 



When the same yeast was fed separately, 0.6 gram per day 

 per rat was required to secure normal growth. Two out of 4 

 females on this diet produced young (total of 3 litters) but all the 

 young were destroyed by the mothers. 



A dried brewer's yeast prepared by us from a wet mixture of 

 bottom yeast and wort secured from a local brewery produced 

 only about one-half normal growth when fed as high as 10 per 

 cent, of the diet, but when these rats were transferred to a mixed 

 diet of grains and milk their growth curves rose sharply towards 

 the normal. When the same yeast was fed separately to other 

 rats at the rate of 0.2 and 0.4 gram per day per rat the results 

 were little better than when the yeast was incorporated in the 

 diet at the rate of 10 per cent. There was no reproduction. 



Sac char omyces cerevisice was grown by us in a wort of malt 

 extract which also contained a little extract of hops. The filtered, 

 washed yeast was air-dried. When fed at the rate of 0.2 gram a 

 day as a supplement to the basal vitamine-B-free ration the rats 

 made a continuous slow growth but the mature rats were under- 

 sized, the males averagin g about 200 grams and the females about 

 160 grams. One female had 2 litters, but the young all died in the 

 first case and in the second case they were so poorly nourished 

 that they had not left the nest after 4 weeks. These young rats 

 later died in convulsoins after they had become large enough to 

 eat their mother's ration. 



Young rats fed a dried distiller's yeast at the rate of 0.2 gram 

 daily made poor growth or none at all during a period of 4 weeks. 



