BIOLOGICAL RELATIONS BETWKKX CAROTINOIDS 193 



results not only confirmed the findings of Willstatter and Escher 

 (1912) as to the xanthophyll character of the major pigment of egg 

 yolk, but demonstrated as well that the same pigment is found in the 

 blood serum and adipose tissue. The results of the earlier studies on 

 the origin of the carotin in cattle naturally suggested that the xantho- 

 phyll in the tissues of the fowl and in the yolks of its egg is similarly 

 derived from the xanthophyll of the food. This was demonstrated to 

 be the case in carefully controlled feeding experiments in which a 

 xanthophyll-rich ration (containing an abundance of yellow maize), 

 a carotin-rich ration (containing an abundance of carrots) and a 

 carotinoid-poor ration were fed to laying hens. The yolks of the 

 eggs increased materially in color on the xanthophyll-rich ration, and 

 the blood serum was also rich in pigment, but there was a marked 

 decline in the color of the egg yolks from the hens on the carotin- 

 rich and carotinoid-poor rations which was practically parallel and 

 which was accompanied by almost carotinoid-free blood serum. The 

 experiments showed very clearly, however, that there is not an abso- 

 lute exclusion of carotin by the hen; the egg yolks, adipose tissue and 

 blood scrum always contained a small proportion of the total pigment 

 in the form of carotin, which was clearly somewhat greater in the yolks 

 of the eggs from the carrot-fed hens. 



These experiments on the biological relation of the carotinoids of 

 fowls to the carotinoids of the food found complete confirmation in 

 the experiments of Palmer and Kempster (1919 a, b, c) in which a 

 flock of White Leghorn fowls was raised to maturity from the time of 

 hatching on rations so devoid of carotinoids that the mature birds 

 showed only the merest traces of pigment in adipose tissue and no 

 demonstrable amounts in the blood serum or skin and none in the 

 yolks of the eggs laid by the mature hens. Xanthophyll-rich feeds 

 brought about a rapid coloration in all parts of the body and in the 

 egg yolks (except in the case of laying hens when the egg yolks only 

 were colored) while carotin, fed in the form of highly colored 

 (colostrum) butter fat had practically no effect on the color of the 

 bird's tissues. 



It was found in connection with the writer's (1914e) milk fat 

 studies that the pigment of human milk fat consists of both carotin 

 and xanthophyll. By analogy with the cattle experiments it was con- 

 cluded that the lipochromes in the human body are likewise derived 

 from the carotinoids of the diet. Hess and Myers (1919) later demon- 

 strated this to be the case in experiments in which it was shown that 



