VITAMIN E 337 



Proof of the Existence of Vitamin E 



Considerable hesitancy was at first shown by various investigators 

 (Hogan and Harshaw, 1924; Anderegg, 1924; Anderegg and Nelson, 

 1925, 1926; Nelson et al., 1926) in regard to the existence of a new 

 fat-soluble vitamin essential to reproduction. One reason for this was 

 undoubtedly the failure to carry out in every detail the technique which 

 Evans and his collaborators emphasized as essential in differentiating 

 sterility due to lack of vitamin E from that induced by other causes. 

 Another ground for hesitancy in accepting the vitamin hypothesis for 

 this type of sterility was the failure to understand the significance of 

 the so-called "initial fertility" on diets supposedly lacking in vitamin E. 

 As noted by Evans and Bishop in their early reports, there may be a 

 high percentage of fertility in the first gestation of such a group of rats, 

 but second and subsequent gestations show increasing sterility. Younger 

 animals show greater fertility than older ones on the same deficient 

 diet and there may even be seasonal variations in fertility. Two factors 

 were considered to be chiefly responsible for initial fertility on diets 

 supposed to be free from vitamin E — the transmission of a part of the 

 mother's store of vitamin E to her offspring during gestation and the 

 inclusion unwittingly of vitamin E in the basal diet in traces which may 

 vary seasonally. 



Evidence of the existence of a vitamin having the properties de- 

 scribed by Evans and Bishop was soon forthcoming in two other 

 laboratories where investigations which had been proceeding for some 

 time with quite different objectives from those of Evans led to the 

 same conclusion. Sure, at the Arkansas Agricultural Experiment Sta- 

 tion, during the course of an investigation begun in 1919 on the amino 

 acid requirements for reproduction, encountered a dietary sterility in 

 his experimental rats which could not be prevented or cured by the 

 addition of any of the known vitamins or amino acids or by improving 

 the salt mixture. The addition of a plant material, even from a single 

 source such as the Georgia velvet bean pod meal, rice, corn, or oats, to 

 a sterility-producing diet, resulted in fertility. With the announcement 

 by Evans and Bishop of the existence of a hitherto unrecognized dietary 

 factor essential for reproduction, it became evident to Sure (1924, 

 1924a) that the materials which he had found eflfective in preventing 

 sterility owed this property to the presence of this same vitamin. 



Meantime Mattill and his associates at the University of Rochester, 

 during the course of an extensive investigation (also initiated in 1919) 

 of the nutritive properties of milk, had reported as early as 1920 (Mat- 



