414 THE BIOCHEMISTRY OF B VITAMINS 



curative factors is undoubtedly due to the fact that the substances in- 

 volved are closely related to one another metabolically, and various con- 

 siderations may eventually cause the folic acid group and vitamin B i2 

 to be considered as a functional unity. 



It is important to realize that the afflictions considered here have been 

 recognized for a great many years; they are widespread, and in terms 

 of their overall effects they compete with beriberi and pellagra as avita- 

 minoses: it is for that reason that their discussion occurs at this point. 

 As a consequence, the consideration of these conditions upon which numer- 

 ous volumes have been written must be extremely abbreviated. Further, 

 the discoveries of the folic acid group of substances and vitamin Bi 2 and 

 their remarkable clinical efficacy have been so recent that there is at the 

 time of writing a considerable degree of uncertainty and even confusion 

 regarding the true picture of their function. The metabolic function of 

 these vitamins, discussed elsewhere (p. 198), is at present only poorly 

 understood. 113a For these reasons it seems best to present in barest outline 

 form the facts as they now stand, realizing full well that in these para- 

 graphs more than any other, the overall concept may change drastically 

 within a few months. 



The following clinical conditions have been found to respond in some 

 degree to one or both of the vitamins here discussed: 



(a) Addisonian pernicious anemia. 



(b) sprue 



(c) nutritional macrocytic anemia 



(d) macrocytic anemias of pregnancy 



(e) macrocytic anemias (megaloblastic) of infancy 



(f) macrocytic anemias following surgery, alcoholism, cancer, and 

 infectious agents. 



In addition, thymine (5-methyluracil) in massive doses has been found 

 to be effective in a number of these conditions. 







CH 3 



HN I 

 H 



thymine 



It seems most convenient to discuss the effects of these vitamins and 

 thymine in relation to each of the conditions mentioned above, and in 

 the approximate order given. 



