132 THE VITAMINS 



Goldberger and his coworkers (1926) found an 85 per cent alcohol 

 extract of corn meal, and Sherman and Sandels (1929) an 80 per cent 

 alcohol extract of ground whole- wheat, good sources of vitamin B 

 (Bi) very deficient in vitamin G (Bo). 



In developing their method for the determination of vitamin G 

 (Bo) Chick and Roscoe (1928) obtained evidence that casein purified 

 by washing with acidulated water and prolonged heating at 120° C. 

 still contains considerable amounts of vitamin G, an observation con- 

 firmed by the report of Goldberger and his associates (1930) to the 

 effect that casein still may have pellagra-preventing value after being 

 leached in acidulated water for a week with the water changed daily. 

 By prolonged extraction with 0.05 per cent acetic acid, followed by 

 extraction with 50 or 70 per cent acidified alcohol, drying and roasting 

 for 3 days at 120° C., Chick and Roscoe believe they can render their 

 casein practically free from vitamin G (B2). 



These investigators prepare their test animals for vitamin G meas- 

 urements by confining them to a diet presumably free from all water- 

 soluble vitamins for a week to 10 days, after which they transfer them 

 to separate cages with raised screen bottoms and supply a daily dose of 

 Peters' antineuritic concentrate, to which the animal generally responds 

 by a temporary increase in weight. After 3 or 4 weeks from the begin- 

 ning of the experiment, the material to be tested for vitamin G is 

 given in graded doses, and the minimum dose permitting an average 

 weekly increase of from 10 to 12 grams during a 2- to 4-week experi- 

 mental period, is taken as a standard of comparison. 



In the experience of Chick and Roscoe concordant results can be 

 obtained so long as the animals used have not been kept longer than 

 6 to 7 weeks on the deficient diet, and they held that each animal 

 could be satisfactorily used for two successive test periods of 2 or 

 3 weeks each one after the other if the second dose of vitamin- 

 containing material were larger than the first or after a 2-week 

 depletion period in case the succeeding dose were smaller than the 

 first. 



Aykroyd and Roscoe (1929) noted that young rats when first caged 

 singly and put on a strange diet may make very little growth during 

 the first week, even on a good diet. They therefore disregard the first 

 week's growth, and use as the standard for comparison the average 

 weekly growth during the following four weeks, the relative vitamin 

 G (Ba) values of foodstuffs being estimated from the minimum 

 amounts required daily to maintain a weekly gain of 11-14 grams during 

 those weeks. They use male and female test animals in approximately 



