INTRODUCTION 



however, whereas incubation of the L. casei factor with fresh chick 

 liver caused a marked increase in the folic acid content as measured 

 by S. faecalis R}^ The increase was twice as great when pyracin 

 (page 336) was present in the incubation mixture. This action of 

 pyracin is believed to be due either to conjugation with the L. casei 

 factor or to its incorporation into an enzyme system that brings 

 about the conversion of the L. casei factor to folic acid. 



Vitamin Be 



A fifth factor, closely related to both folic acid and the three 

 L. casei factors, was described in 1939-40 by A. G. Hogan and E. M. 

 Parrott.^2 jj^js ^as prepared from liver by a process involving 

 adsorption on fuller's earth followed by elution. It was iomid to 

 correct a hyperchromic macrocytic anaemia in chicks, and, in conse- 

 quence, was named " vitamin Be " the suffix indicating its associa- 

 tion with the nutrition of the chick. Further purification of vitamin 

 Be was effected by A. G. Hogan and his colleagues, ^^ who pointed out 

 that the factor had properties very similar to those of the liver L. casei 

 factor. Isolation of the pure factor ^* and a comparison of its pro- 

 perties with those of the L. casei factor confirmed this close relation- 

 ship. Moreover, crystalline vitamin Bc^^ maintained normal growth 

 and feathering in chicks in addition to preventing the development of 

 a macrocytic hyperchromic anaemia, leucopenia and thrombocyto- 

 penia, whilst the purified folic acid of H. K. Mitchell and R. J. 

 Williams ^® also stimulated the growth of chicks. 



Further work on vitamin Be, however, revealed a state of affairs 

 comparable with that obtaining in the case of the L. casei factor, 

 vitamin Be concentrates differing in their biological activities accord- 

 ing to whether they were produced from liver or from yeast. Binkley 

 et al,^'^ for example, found that vitamin Be concentrates prepared 

 from yeast almost completely failed to stimulate the growth of L. 

 helveticus, but they became highly active following enzymatic diges- 

 tion ; from such digests a crystalline compound was isolated that 

 stimulated the growth of both L. helveticus and S. faecalis R and also 

 cured the anaemia and increased the growth rate of chicks. They 

 accordingly reserved the name vitamin Be for the liver factor, and 

 gave the name vitamin Be conjugate to the factor present in yeast. 



Later, this same group of workers reported^® the isolation of 

 vitamin Be conjugate in crystalline form and confirmed its ineffective- 

 ness as a growth factor for L. helveticus and S. faecalis R and its 

 ability to cure a nutritional macrocytic anaemia in chicks. After 

 digestion with an enzyme preparation made from hog kidney, the 

 crystalline factor, like the crude factor previously described, yielded 



459 



