392 MISSOURI AGRICULTURAL EXP. STA., RESEARCH BULLETIN NO. II 



The establishment of the chemical identity of the pigment of 

 milk fat and of its simple physiological relation to the carotin and 

 xanthophylls of green plants at once opened the question of a sim- 

 ilar relation of the pigment which is so often observed in the body 

 fat of cows, especially those of certain breeds, such as the Jersey and 

 Guernsey. The question is also raised as to the presence of xan- 

 thophylls in the corpus luteum pigment. In addition an interesting 

 question is opened as to whether the yellow skin secretions of cer- 

 tain breeds of dairy cows, which is often interpreted as indicating 

 the ability of these animals to secrete yellow milk fat, is also due 

 to the same pigments that characterize the butter fat. 



The present investigation was undertaken for the purpose of 

 studying these questions. In addition some information was gathered 

 relative to the relation of the breed of the cow to the amount of color 

 found in the body fat. 



METHODS OF IDENTIFICATION. 



The general methods of studying and identifying the pigments 

 of the body fat, corpus luteum and skin secretions of the cow were 

 the same as were used in the study of the pigment of milk fat.. A 

 detailed account of these methods may be found in the preceding 

 paper of this series, which deals with the milk fat pigment. 



These methods were a study of what we have called the spec- 

 troscopic, solubility, and adsorption properties of the pigments. The 

 methods were confined to characteristic, physical and chemical prop- 

 erties of the pigments for the same reasons that they were used for 

 the study of the milk fat pigment, namely because, in the case of the 

 body fat at least, the very large amount of fat with which the pig- 

 ments are associated precludes their isolation in sufficient quantity 

 for chemical analysis. In the case of the pigments of the corpus 

 luteum and skin secretions not enough material was available for 

 isolating any great quantity of pigment. 1 



The Spectroscopic Properties. It was found that carotin and 

 xanthophylls isolated from green alfalfa hay, carrots or other plants 

 rich in these pigments showed characteristic absorption bands when 

 viewed in a spectroscope of narrow dispersion. When the spectro- 

 scope was set at an arbitrarily chosen standard, each class of pig- 

 ments exhibited bands in characteristic position, especially in carbon 

 bisulphide solution, and could then be readily identified. The arbitrary 



1. Escher succeeded in isolating less than 0.5 gram of impure crystals of 

 corpus luteum pigment from 10,000 cows' ovaries. 



