4l6 MISSOURI AGRICULTURAL EXP. STA. RESEARCH BULLETIN NO. 12 



we have shown that the yellow lipochromes of the milk fat and body 

 fat of cows are also composed principally of carotin, altho both have 

 associated with them one or more minor xanthophyll constituents. In 

 addition we have shown conclusively that these pigments originate 

 from the food of the cow. They are therefore not products of animal 

 synthesis but merely substances assimilated with the digestion products 

 of the food and subsequently secreted in the milk fat or laid up in the 

 body fat. The studies leading to these results are given in the two 

 preceding papers of this series. 1 



Up to this time the experimental evidence pointing to the above 

 stated physiological relation between the carotin and xanthophylls of 

 plants and the pigments of butter fat and body fat has been based upon 

 feeding experiments in which the relation between the amount of these 

 pigments in the food and the color of the milk fat and body fat was 

 carefully studied. It was recognized however that the evidence would 

 not be absolutely complete until the means of transporting the food 

 pigments to the milk fat and body fat could be established. A 

 close study of the yellow lipochrome of the blood serum, in a man- 

 ner similar to the preceding studies of the milk fat and body fat 

 pigments, naturally seemed to offer the most ready means of establish- 

 ing the physiological relation between the plant pigments and the lipo- 

 chromes of milk fat and body fat. 



The present investigation was therefore undertaken for the pur- 

 pose of studying the yellow lipochrome of the blood serum in 

 regard to its chemical and physiological relations to the carotin and 

 xanthophylls of green plants and to these pigments when found in the 

 milk fat and body fat of the cow. It was believed that this investigation 

 would serve the twofold purpose of establishing the connecting physi- 

 ological link between these plant and animal pigments and also scien- 

 tifically classifying the blood serum lutein of the cow which pigment 

 has never been the subject of close investigation. 



METHODS OF IDENTIFICATION. 



The methods used for identifying the pigment of the blood 

 serurn were the same as were used in the study of the milk fat and 

 body fat pigments. They consisted in the application to the isolated 

 pigment of the characteristic physical and chemical properties of 

 carotin and xanthophylls. These properties were the position of the 

 spectroscopic absorption bands, the relative solubility toward petroleum 

 ether and 80 to 90 per cent alcohol, and the adsorption affinity toward 



1. Also Jour. Biol. Chem. 17, No. 2, pp. 191, 211 (1914). 



