VITAMIN B (Br) 63 



rats, because the basal diets and the bodily store of the rats may have 

 provided the other essential factors in variable amounts and propor- 

 tions. Tests for the presence of vitamin B (Bi) may have failed or its 

 true concentration may have been underestimated because other nutri- 

 tive essentials v^^ere furnished by the food or bodily store in concentra- 

 tions too low to support the rate of grovi^th permitted by vitamin B 

 (Bi). It is of interest that Guha and Drummond (1929) in the frac- 

 tionation of vitamin Bi concentrates, have observed no fixed ratio 

 betv^een the rat-dose and pigeon-dose of the various preparations inves- 

 tigated. Thus the rat-doses of their picrolonic filtrate, of the phospho- 

 tungstic fraction and of the platinic chloride fraction were respectively, 

 10 times, 7 times, and 3 times the pigeon-dose. These authors are in- 

 clined to attribute this difference to the errors in the biological methods 

 of assay rather than to a difference between the rat-factor and pigeon- 

 factor. But the fact that both their rat experiments and pigeon experi- 

 ments appear to corroborate a duality of the nature of the antineuritic 

 Bi raises the question as to whether various investigators even when 

 using curative tests in pigeons were all dealing with the same factor. 

 Certainly we have not adequate reason to assume that preventive or 

 curative tests measure the factor necessary for weight-maintenance 

 in pigeons, or that the first two are necessarily identical. 



With the definite acceptance of at least two factors in growth- 

 promoting vitamin B (the relatively heat-labile B (Bi) and heat-stable 

 G (B2)), attention was paid to their distribution in the various steps 

 in the fractionation process for concentrating vitamin B. 



In 1928, Salmon, Guerrant and Hays noted that fuller's earth, par- 

 ticularly when used in low concentrations, adsorbs vitamin B prefer- 

 entially from a solution containing both vitamins B and G (B2) even 

 though vitamin G is preponderant in the original solution. Fractionation 

 of the vitamin G-rich filtrate left after three successive adsorptions, 

 with alcohol to a concentration of 51 per cent by weight yielded a pre- 

 cipitate which was rejected; concentration of the resulting filtrate and 

 washings and precipitation at an alcohol concentration of 82.7 per cent 

 gave a fraction comparable to the Osborne-Wakeman fraction II, which 

 carried a large part of the vitamin G originally contained in the crude 

 extract, and which on the basis of total net solids appeared to have 3 to 

 4 times the original concentration of vitamin G. This precipitate was, 

 however, less rich in vitamin B than the filtrate left after the frac- 

 tionation. 



The effect of hydrogen-ion concentration upon the adsorption of 

 vitamins B and G by fuller's earth from extracts of maize and yeasts 



