VITAMIN G (B^) 135 



weeks. In one investigation conducted under these modified conditions, 

 between 80 and 90 per cent of the animals (124 cases) maintained 

 fairly uniformly the restricted rate of growth during the first four 

 weeks, but only about 20 per cent could maintain this same rate of gain 

 throughout an 8- week experimental period. Usually between the fifth 

 and seventh week of the experimental period, the growth curve tended 

 to flatten ; often the animals thereafter merely maintained their body 

 weight, or suflfered a decline. In view of this fact, and the findings that 

 the least variability in response is encountered in the early weeks of 

 the experimental period, it is tentatively suggested that all quantitative 

 determinations be based on a 4- or 5-week experimental period. If, as 

 sometimes happens, the animal declines in weight during the first week 

 or so of the test period, while adjusting itself to new conditions, it is 

 suggested that the animal be weighed two or three times weekly, until 

 the minimum body weight has been found, and the experimental period 

 be counted as beginning at that point and continued throughout the 

 following four weeks, the rate of growth being restricted by vitamin 

 intake, as suggested by Bourquin, to three or five grams per week. 



Quantitative Studies of Some Properties of Vitamin G 



Sherman and Sandels (1929, 1931) studied quantitatively the solu- 

 bility of vitamin G in neutral alcohol of certain concentrations. As 

 their results showed that relatively more of this vitamin can be ex- 

 tracted from ground whole wheat than from dried bakers' yeast by 80 

 per cent (by weight) alcohol, it would seem necessary to consider the 

 physical and chemical nature of the source material as well as the sol- 

 vent and method of extraction in evaluating the evidence regarding 

 the solubilities (more strictly speaking, extractabilities) of these vita- 

 mins. 



The essentials of their method of extraction were as follows : 400 

 grams of air-dry material was treated with 1,500 cubic centimeters of 

 alcohol, thoroughly stirred and allowed to stand at room temperature 

 (20° to 25° C.) for 24 hours; then filtered with suction and the residue 

 washed on a Biichner filter with 750 cubic centimeters of alcohol of the 

 same strength; again stirred with 1,500 cubic centimeters of the alcohol, 

 allowed to stand 24 hours, filtered and washed as before. The residue 

 was dried in the air at room temperature. The extract obtained by com- 

 bining the two filtrates and the washings was concentrated on the steam 

 bath and evaporated at room temperature on cornstarch. 



This treatment of dried yeast with 95 per cent alcohol did not 

 measurably diminish its vitamin G potency; the residue appeared as 



