VITAMINS 345 



cells. An anemia of this kind is sometimes associated with pellagra, 

 pregnancy, and the tropical disease called sprue. During World War 

 II wide use of sulfa drugs to prevent infection after injury also 

 eliminated the normal intestinal bacteria that synthesize folic acid. 

 In some areas of the Pacific the available diets were low in folic acid, 

 and deficiency anemias developed in hospitals before the role and 

 distribution of the vitamin were as well known as they are today. 



Folic acid prevents and cures characteristic anemias in rats, chicks, 

 and monkeys. It is essential for lactation in rats and hatchability of 

 eggs as well as for normal growth of chicks, turkeys, and guinea pigs. 

 Hence this vitamin is probably essential for all the higher animals at 

 least. 



Sulfa drugs prevent growth of many bacteria by acting as antago- 

 nists for p-aminoben/oic acid and blocking the formation of folic acid. 

 Thus they can be used to prevent or reduce infections before the 

 animal as a whole develops serious deficiency symptoms. Analogues 

 are also known for folic acid itself. Although these compounds are 

 rather toxic for general clinical application, one has been used to 

 produce temporary remissions of acute leukemia. This drug, aminop- 

 terin, also causes partial recessions of certain experimental tumors but 

 is not particularly effective on human cancers. 



VITAMIN B 



12 



This rather recently isolated member of the water-soluble group 

 of vitamins is also called cobalamine and is unique among vitamins 

 in containing a metal atom. Although not proved in all respects, the 

 presently accepted structure is based on extensive physical and chem- 

 ical data. The two bonds represented by dotted lines lie along the 

 axis perpendicular to the plane of the paper. This extremely com- 

 plicated molecule has not been synthesized. For clinical and experi- 

 mental use it is isolated at a cost of 25<ji/ixg. from certain mold 

 cultures grown in the production of antibiotics. Related compounds 

 have been isolated and studied to a limited extent. 



Vitamin B12 is very low in plants which may not make appreciable 

 use of it. It apparently occius in all animal tissues. Since animals are 

 not known to synthesize it, they must depend for their supplies on 

 other animals or on microorganisms. Strict vegetarians may develop 

 marginal deficiencies if their intestinal flora are disturbed or if such 

 animals are fasting. Ruminants are not known to become deficient 

 because of the vitamin supplied by the bacteria of the rumen. Thus 



