270 CAROTINOIDS AND RELATED PIGMENTS 



Stcenbock has been forced to abandon his position that the two sub- 

 stances may be identical and to admit that their "coincident occurrence 

 in nature might be due to physiological determination, pure and sim- 

 ple." The attempts to show some correlation between the color of 

 perinephritic beef fat and vitamin A content in the same paper are not 

 especially convincing on close examination, especially when the results 

 are compared with butter fat of like color fed at much lower levels. 

 In addition, the statement is made that egg yolks of a light color but 

 with a normal vitamin content can be produced on specially selected 

 rations, which confirms the observations of Palmer and Kempster 

 (1919b) and Palmer and Kennedy (1921). 



The lack of correlation between pigmentation and vitamin content of 

 animal fats was first pointed out by Drummond and Coward 2 (1920) 

 for butter fat and a large number of other fats and oils (including 

 vegetable oils). It is of interest that colorless dog fat and colorless 

 perinephritic pig fat were relatively rich in vitamin A. Miss Stephen- 

 son (1920) further corroborated this by decolorizing butter fat with 

 charcoal without impairing in any way its vitamin content. This ex- 

 periment, however, requires confirmation, primarily because of the re- 

 markably small amount of charcoal which was used. As stated in 

 Chapter IX, the writer has not yet succeeded in duplicating these de- 

 colorizations with only 2.5 per cent of any decolorizing carbon which 

 he has been able to secure. 



Further proof that vitamin A is not necessarily associated with 

 carotinoids was furnished by Palmer and Kennedy (1921) who found 

 that albino rats grew normally and reproduced on diets in which prac- 

 tically carotinoid-free ewe milk fat (containing 0.00014 per cent caro- 

 tin) furnished the vitamin A in the ration at levels of 5 to 9 per cent, 

 and that similar results followed the use of carotinoid-free egg yolk 

 produced by hens on diets made up of selected white corn, skim milk, 

 pork liver (about 10 per cent) and grit. With the rations containing 

 carotinoids, the best results were secured with only 0.126 parts 

 of carotinoid per million of ration. This is very much less pigment 

 than Drummond or Miss Stephenson fed to rats without success. In 

 opposition to this result Steenbock, Sell, Nelson and Buell (1920) have 



2 Previous to this, Rosenheim and Drummond (1920) were much attracted by the 

 idea of an intimate relationship between carotinoids and vitamin A, and abandoned 

 it very reluctantly when they were unable to establish an identity of vitamin A with 

 either carotin or xanthophyll. Van den Bergh, Muller and Broekmeyer (1920) have 

 also supported Steenbock's theory, without, however, submitting it to experimental 

 verification. 



