VITAMIN B (B,) 35 



vitamin fractions of yeast and rice polishings may have been due in 

 part to this isomeric form of nicotinic acid. 



Harden and Zilva (1917), repeating WiUiams' experiments with 

 a-hydroxypyridine, were able to confirm the chemical properties of 

 that substance as reported by Williams but were unable by its use 

 to effect a cure or even an improvement in the condition of the poly- 

 neuritic birds. Pure adenine, as well as adenine treated with sodium 

 ethylate in a sealed tube for five hours at 100° C, also yielded negative 

 results in agreement with Voegtlin and White but in disagreement with 

 Williams and Seidell. 



Meantime the water-soluble, growth-promoting factor for rats con- 

 sidered by many to be identical with the antineuritic vitamin was re- 

 ceiving an increasing share of the attention of investigators, and no 

 further report on the attempted isolation of the antineuritic vitamin 

 as such was noted until May 1920, when Myers and Voegtlin re- 

 ported the results of an investigation covering a period of several years 

 in which they had used autolyzed yeast as a starting material, and 

 mastic, Lloyd's reagent and ferric phosphate as adsorbing agents, but 

 with little success. 



The method adopted by Myers and VoegtUn consisted in the extraction of 

 dried brewers' yeast by 95 per cent methyl alcohol containing 2 cubic centimeters 

 of concentrated hydrochloric acid per liter and the precipitation of the purine 

 fractions by hot silver acetate and of the active substance by barium hydroxide 

 and silver acetate. A further concentration was efifected by decomposing this 

 precipitate with hydrogen sulfide, and precipitating most of the histidine fraction 

 with mercuric sulfate, and the active material with absolute alcohol. This pre- 

 cipitate, on decomposition as before, yielded a filtrate which, after concentration 

 in vacuo at low temperatures, gave a purple solution with ninhydrin, a negative 

 biuret test, and no precipitate with picric acid, but gave a heavy precipitate with 

 phosphotungstic acid, and was highly curative for polyneuritic pigeons. The solu- 

 tion on further concentration in vacuo over soda-lime yielded spindle-shaped crys- 

 tals which were active as long as the mother liquor was present. On drying, the 

 crystals changed from spindles to prisms and became inactive. When the prisms 

 were dissolved in a relatively large volume of water and again allowed to crys- 

 tallize, spindle-shaped crystals were again formed. While realizing that the activity 

 might be in the non-crystallizable mother liquor as well as in the crystals, Myers 

 and Voegtlin were of the opinion that there were at least two substances in the 

 final solution, both of a distinctly basic character. One of the impurities was a 

 histamine-like substance as shown by the positive Pauly reaction. 



Hofmeister (1920) in an attempt to separate the antineuritic sub- 

 stance from commercial rice meal made use of bismuth potassium iodide 

 as precipitant. 



The material was first shaken with 80 per cent alcohol, and the extract dis- 

 tilled in vaaw to a thick sirup, acidified with 3 per cent hydrochloric acid and 

 shaken with ether. The aqueous fraction, after removal of the ether, was again 

 evaporated to a thick sirup and the extraction with 80 per cent alcohol repeated. 

 After the alcohol had been expelled, the extract was made slightly alkaline with 



