244 THE VITAMINS 



The above theory at first received the support of Rosenheim and 

 Drummond (1920). The failure of hpochromes to serve as sources of 

 fat-soluble A as previously noted by Drummond (1919a) was con- 

 sidered to justify the conclusion that the lipochrome pigments and 

 vitamin A are not identical but not to refute the theory of a close rela- 

 tionship between them. Later Drummond and Coward (1920a) sub- 

 jected this theory to the test of comparing a large number of animal 

 and vegetable oils as to their relative richness in vitamin A and in 

 lipochrome pigments. The lack of relationship between the pigmentation 

 of the 24 fats examined and their richness in vitamin A led them to 

 conclude that "unless we assume the existence of a leuco-form it does 

 not appear probable that the fat-soluble vitamin is a member of the 

 lipochrome class of pigments. The frequent association of the growth 

 factor with pigments of that type must therefore be regarded as acci- 

 dental." In this they agreed with the conclusions of Palmer and Kemp- 

 ster (1919, 1919a, 1919b), who reported success in raising a large 

 number of White Leghorn fowls from hatching to maturity on rations 

 which contained at the most mere traces of carotinoids. Hens on this 

 ration laid eggs which were practically free from pigments and from 

 which normal chickens were hatched. Furthermore Stephenson (1920) 

 found that a crude (alcohol-light petroleum) extract of dried carrot 

 when added to a fat lacking in vitamin A conferred upon it growth- 

 promoting properties and protected rats from xerophthalmia while pure 

 carotene extracted from carrots was without efifect. Moreover, butter 

 from which the coloring matter had been completely removed by filtra- 

 tion through charcoal did not lose its growth-promoting properties. 



The earlier literature on this subject was subjected to an extensive 

 and critical review by Palmer, Kennedy and Kempster (1921) who 

 opposed the idea of identity or relationship between vitamin A and 

 carotinoids. They not only reported a complete absence of carotinoid 

 pigments in the albino rat, the experimental animal used in most of the 

 biological studies on vitamin A, but were able to report growth and 

 reproduction of rats with ewe milk fat containing only 0.00014 per 

 cent carotene, as the sole source of vitamin A, the ration showing the 

 best results containing only 0.0000126 per cent carotene. Growth and 

 reproduction were also obtained with rats using carotinoid- free &gg 

 yolk as the sole source of vitamin A. Quantitative comparisons were 

 made of the carotene content and vitamin A efificiency of various 

 rations as reported in the literature, and the conclusion was drawn that 

 carotene and vitamin A are not quantitatively associated in the plant 

 tissues in which both were presumed to be synthesized. The existence 



