192 NUCLEIC ACIDS AND THE NITROGENOUS BASES 



phoric acid and sodium tungstate. A similar color is yielded by uric 

 acid, alloxantin, dihydrophenylalanine, amino-tyrosine, and certain 

 di- or tri-phenols, but not by purine or pyrimidine bases other than 

 those mentioned, nor by tyrosine itself. 



The curative substances isolated by Funk have been termed by him 

 Vitamines. From rice-polishings a crystalline curative fraction was 

 obtained which, on fractional crystallization was separated into two 

 substances. The one proved to be Nicotinic Acid, which, in the pure 

 crystallized condition, is devoid of curative action, and the other an 

 unidentified nitrogenous substance which tends to lose its curative 

 power with successive purifications. The curative substance from 

 yeast was similarly found to yield nicotinic acid and an unknown 

 nitrogenous base. 



From the fact that some of the pyrimidine derivatives have a weak 

 curative action on polyneuritis, it was at first thought that the vita- 

 mines were probably pyrimidine derivatives. The more recent 

 investigations of R. R. Williams indicate that the curative principles 

 may be substances having a Betaine structure. Thus a-Hydroxy- 

 pyridine has a definitely curative action upon artificially induced poly- 

 neuritis, so long as it yields needle-shaped crystals, but these crystals 

 spontaneously change, on standing, into crystalline granules which are 

 quite devoid of antineuritic properties. Now a-hydroxypyridine may 

 conceivably exist in a variety of chemical forms of which the following 

 are examples : 



:H \ / CH \ 



\ / \ 



HC CH HC CH 



HC Cx HC COH 



The curative variety, yielding needle-shaped crystals, is probably 

 the pseudobetaine form, resembling the betaines in containing the 

 group: 



_N O 



I 



and the fact that this structure and the antineuritic properties of 

 a-hydroxypyridine spontaneously disappear on standing is suggestive 

 in view of the fact that the curative substances isolated from yeast 

 and rice-polishings by Funk tend also to lose antineuritic power 

 spontaneously on standing or on repeated purification. 



The betaines themselves, such as trimethylglycine or trigonellin 

 are impotent to protect pigeons fed on polished rice from the develop- 

 ment of polyneuritis. It is, however, characteristic of the betaines 

 that the anhydride ring is very unstable and readily opens up, as, for 



