A CRITICAL INVESTIGATION AND AN APPLICATION 
OF THE RAT GROWTH METHOD FOR THE 
STUDY OF VITAMIN B. 
INTRODUCTION 
The term “vitamin B” is here used synonomously with 
“water soluble B” as a designation for the water soluble 
growth promoting substance whose existence as an essential 
constituent of the food was demonstrated by Hopkins* ®& 2, 
Osborne and Mendel *’, and McCollum and Davis *" by 
growth experiments with young mammals, chiefly rats. 
Whether this is identical with the antineuritic substance stud- 
ied by Ejijkman??*4, Funk 1°16, Williams?*7?° and others 
through experiments with birds, or with the “bios” of Wil- 
diers *4 which shows a growth promoting property toward 
yeast, does not concern the present investigation. ‘The recent 
publication of a monograph The Vitamins by the American 
Chemical Society * makes it unnecessary to review previous 
work at length in this connection. 
The importance of vitamin B as a factor in food values 
makes desirable the standardization of the method of studying 
this substance so as to permit of quantitative investigation of 
the relative amounts in different foods or in the same food 
before and after heating or other treatment to which foods 
may be subjected in the course of preservation or cooking. 
When such methods are sufficiently developed they can 
also be applied to the quantitative measurement ‘of the concen- 
tration of the vitamin at successive steps in attempts to iso- 
late the substance from natural sources and bring it to a con- 
dition of maximum purity for the determination of its chemi- 
cal nature. 
For the present investigation white rats were selected as 
the experimental animal and dried skimmed milk as the vita- 
min-containing food. Examination of the literature, as well 
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