54 THE VITAMINES 



inoculating Nageli's solution with a needle-point of yeast . culture, 

 preparing at the same time the necessary controls. The cells are 

 counted after 5 to 6 hours and again after 20 to 24 hours. From 

 20 to several thousands of cells could develop from a single cell in 

 24 hours, depending upon the vitamine concentration. Williams 

 undertook some problems with the help of this method, for example, 

 the protective influence of fat upon the destruction of vitamines by 

 alkali. Vitamine extracts, prepared with acid or alkali, appeared 

 to be best utilized by yeast. The greatest influence was obtained by 

 a preparation made by shaking yeast with fuller's earth. The ac- 

 tive substance was also shown to be present in the alcoholic extract 

 of protein-free milk, wheat embryo, and pancreatin, and in the 

 decomposed phosphotungstic acid fraction from yeast. Casein 

 and lactose were likewise active, although in the former the ac- 

 tivity was not attributed to the amino acids but to the small amounts 

 of vitamines present. The active substance was partly destroyed 

 by heating in the autoclave for a half hour at one atmosphere. An 

 alcoholic extract of egg-yolk was active while the ether extract 

 containing vitamine A was inactive. The C-vitamine, as we shall 

 note later, appears to have no influence on the growth of yeast. 

 Bachmann (129) investigated the behavior of two kinds of yeast, 

 one apparently " Saccharomyces cerevisiae" and the other, isolated 

 from fermented pears. These two varieties showed a different 

 behavior towards the vitamine solutions. One of the yeasts grew on 

 the surface and was less dependent upon the vitamine addition (in 

 this she indicated the possible analogy of green leaves and influence 

 of oxygen). The Bachmann method is as follows: A yeast sus- 

 pension in a liquid nutritive medium is placed in a sterile fermenta- 

 tion tube, and the COg evolved is measured after a definite incuba- 

 tion period, being compared with controls in which no vitamine was 

 added. Orange juice, yeast extract, peptone, Liebig's meat ex- 

 tract, honey, certain vegetable extracts and milk were tried as a 

 source of vitamine, and the results were for the most part the same 

 as had been found in animal experiments. Certain discrepant re- 

 sults could be explained by the greater sensitivity of the method. 

 Pasteurization and sterilization decrease the activity of milk. It 

 was also interesting in this work to note the different behavior of the 

 two kinds of yeast as to their dependence upon the vitamine addi- 

 tion, one requiring more than the other. Abderhalden and Schau- 



