CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 44! 



B, CAROTIN AND XANTHOPHYLLS DURING DIC-ESTION 



The establishment by us l of both a chemical and physiological 

 relation between the carotin and xanthophylls of plants and the yellow 

 lipochromes of the milk fat, body fat, blood serum and corpus luteum 

 of the cow has shown that it is the carotin that is by far the more 

 important in pigmentation of the animal body. It is a well-known 

 fact that xanthophylls are as abundantly and sometimes more abun- 

 dantly distributed in vegetable matter than carotin. The question 

 naturally arises then, why carotin is the pigment which is principally 

 taken up by the cow's body, and why the xanthophylls appear there 

 only in very small quantity. This seemed to us to be an important 

 physiological question. 



It will readily be recognized that a question of this nature is not 

 easily answered. It may therefore be stated in advance that the results 

 of our studies were not as satisfactory as was anticipated. The 

 data are presented, however, for what value they may possess, since 

 opportunity was not presented for a further study of the question. 

 The data are of some value, at least, in that a number of facts are 

 presented which are sufficiently related to advance a fairly acceptable 

 theory in regard to the question. 



METHODS OF STUDY 



Several methods of study which did not appear to offer many 

 difficulties, seemed available, by which it was thought light could be 

 thrown on the question. One method was to study the action of the 

 various digestive fluids, both natural and artificial, on fresh crude 

 residues of the amorphous carotin and xanthophylls of plants. An- 

 other method was to study the nature of the unsaponifiable pigment 

 extracts at various places along the digestive tract of the cow. A 

 third method was closely related to the second and consisted in a study 

 of the unsaponifiable yellow pigments excreted under conditions where 

 unassimilated or undestroyed carotin and xanthophylls of the food 

 would be likely to appear unchanged in the feces. Lack of time made 

 a thorough study of all the methods impossible so that only the 

 significant features of the results of each study will be given. 



1. Missouri Agricultural Experiment Station Research Bulletins Nos. 10 

 and 11, this Bulletin, p. 415 (1914); Jour. Biol. Chem. pp. 191, 211, 223 (1914). 



