THE ANTIBERIBERI VITAMINE 



201 



cipitate or cloudiness at the beginning of the test. All of the test 

 tubes are placed in the incubator for 20 hours at 30C., after which 

 the cells are inactivated by immersing the tubes in a water bath at 

 70 to 80C. for a few minutes. The contents of the tubes are then 

 quantitatively transferred to centrifuge tubes, the lower part of 

 which is in the form of a capillary, graduated in mm. The tubes 

 are centrifuged for 15 minutes at about 2600 r.p.m., and the volume 

 of cells read on the graduated capillary of the centrifuge tube. The 

 reading should be taken at once, since there is a tendency for the 

 yeast cells to swell up, after a time. The control, without the 

 addition of vitamine, must be subtracted from the reading. 



We found that the controls with yeast alone were quite constant 

 and almost independent of the number of yeast cells in the suspension 



0.5 1.0 



1.5 



2.0 2.5 3.0 3.5 4.0 45 5.0 

 Cc. of yeast suspension 



FIG. 49. EFFECT OF VARYING AMOUNTS OF YEAST SUSPENSION (FUNK-DUBIN) 



used, as may be seen from the curve. Experiments with increasing 

 amounts of autolyzed yeast gave a curve markedly different from 

 that of Williams, but which is perhaps better applicable to the study 

 of natural extracts. We feel that our results have been considerably 

 influenced by the presence of inhibiting substances. For this and 

 other reasons, it appears somewhat premature to estimate the 

 vitamine content of various foodstuffs by the use of these methods. 

 A number of problems were undertaken with the help of the above 

 method, and we shall record some of the results. We showed that 

 analyzed substances, isolated from yeast seven years ago by the 

 author, still retained a definite activity, although they had been 

 recrystallized to constant melting point. On the other hand, nico- 

 tinic acid obtained from yeast was inactive. White polished rice 



