CHAPTER III 



VITAMIN G (B.) 



Differentiation o£ the Water-soluble Growth-promoting 



Vitamins 



Mitchell, in 1919, after referring to the then common belief that 

 the antineuritic and water-soluble growth-promoting vitamins are iden- 

 tical, pointed out that "This belief ranges from positive conviction 

 through tacit acceptance, to a frank weighing of the probabiUties." His 

 paper constituted an excellent review of the Hterature on the subject 

 up to that time with a critical evaluation of the evidence then in hand. 

 According to Mitchell, "The conclusion that the two vitamins are 

 identical seems to be based upon the following grounds. ( 1 ) The distri- 

 bution of the two substances in natural food products is very similar 

 and the correlation between the actual amounts (in as far as these 

 have been measured by biological tests) found in different products 

 appears to be close. (2) The lack of known sources of water-soluble B 

 in the diet of various species of experimental animals seems generally, 

 if not always, to result in symptoms of nerve degeneration and paralysis. 

 (3) Extracts of natural food products possessing growth-promoting 

 properties are said to contain very probably only one indispensable 

 vitamin, though supplementing satisfactorily a ration containing no 

 other possible source of antineuritic vitamin. (4) The solubilities of the 

 two vitamins in the common solvents are said to be identical. (5) At- 

 tempts at isolating the two vitamins have shown that they possess 

 identical precipitants and adsorbents. (6) The stabilities of the two 

 substances, especially to acids, alkalies, and elevated temperatures, seem 

 to be similar if not identical." (It is to be kept in mind that this was 

 published by Mitchell in 1919.) 



In discussing the first point, attention was called to instances in 

 the literature in which the correlation between the distribution of the 

 antineuritic and the growth-promoting factors was not close. This 

 seemed to be particularly the case in green vegetables, roots and tubers, 

 which appeared to contain rich or moderate amounts of the growth- 

 promoting water-soluble vitamin (or vitamins) (Osborne and Mendel, 

 1919, 1919c; McCoUum, Simmonds and Parsons, 1918a; Sugiura and 



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