346 THE VITAMINS 



if the distribution be done with successive fresh portions of the petroleum ether. 

 Further purifications can now be carried out both with digitonin, boihng methyl 

 alcohol, and finally, distillations in vacuo." 



In spite of its great stability toward various reagents, as thus sum- 

 marized, vitamin E has been found to be quite unstable in the presence 

 of certain fats and salts ; and the failure to recognize this led to some 

 of the discrepancies in results in earlier vitamin E studies, and it was 

 through efforts to explain these discrepancies that this instability was 

 finally recognized. 



Anderegg (1924) reported failure of reproduction in rats on a diet 

 consisting of whole milk powder 50, starch 38, lard 10, and salt mixture 

 2 per cent and success when part of the lard was replaced by an equiva- 

 lent amount of dextrin, and concluded that for success in reproduction 

 on synthetic diets the ratio of fat to protein should be kept within cer- 

 tain limits. 



Mattill, Carman, and Clayton (1924) reported similar success or 

 failure, depending upon the proportion of lard in the diet, but did not 

 agree with Anderegg in the interpretation of these findings, stating, 

 "this fact is considered not as evidence against the existence of X [E], 

 as some have held, but as an indication that the amount of X required 

 for normal reproductive functions depends upon the nature of the diet." 



Clayton (1927), working in Mattill's laboratory, conducted a sys- 

 tematic comparative study of a series of rations containing lard for 

 the fat and cod-liver oil for vitamins A and D with a parallel series 

 containing no lard and with separate daily administration of cod-liver 

 oil or with radiation of the animals to furnish vitamin D, and reported 

 that "from observations on several hundred animals, many of them in 

 the third generation, it is clear that the presence of these and perhaps 

 other unsaturated animal fats in the ration seriously interfered with 

 reproduction. Reproduction but not lactation was improved when these 

 fats were omitted. . . . The presence of wheat germ oil in the fat- 

 containing rations favored reproduction and also lactation, especially in 

 skim milk powder rations. Depending on as yet unknown factors various 

 rations differ considerably in their ability to protect vitamin E from the 

 destructive action of unsaturated animal fats." 



The same year Evans and Burr (1927) reported that lard at a level 

 of 22 per cent of the ration destroys or renders ineffective the vitamin 

 E in wheat germ, but not at a lower level {7.7 per cent of the ration). 

 Among other materials tested, hydrogenated cottonseed oil and oleic 

 acid rendered vitamin E ineffective, while butter, cod-liver oil at low 

 concentrations, and stearic acid did not. In this paper they were inclined 



