CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 445 



account for the lack of uniformity where this method of desiccation 

 was not employed. 



No further discussion will be given this study. Mention has been 

 made of it merely because the method seems to be a valuable one, 

 and will warrant further application. 



THE EXCRETED PIGMENTS 



For this study the feces of a cow were examined, in a feeding- 

 experiment where the carotin and xanthophylls were furnished by 

 the feeding of carrots only. The balance of the ration was composed 

 of grain and timothy hay almost free from carotin and xanthophylls. 



The method of demonstrating the character of the pigments 

 in the feces was to desiccate a quantity of fresh feces with plaster 

 of Paris and extract the mass with pure carbon bisulphide. The ex- 

 tract was concentrated and studied spectroscopically, and also by means 

 of a Tswett chromotogramm. The relative solubility properties of the 

 pigments thus found were studied, and also the spectroscopic properties 

 of the pigments thus separated. 



In this way it was found that when the cow was receiving 50 

 pounds of carrots per day, both carotin and xanthophylls were abun- 

 dantly present in the feces. This continued for six days after the 

 carrots were withdrawn from the ration, although it was possible 

 to detect but little xanthophyll during this time. 



DISCUSSION OF RESULTS 



Combining the results of the above experiments, the appearance 

 of carotin in the cow's system when fed in excess may be explained 

 on the ground of its greater stability toward the digestive processes, 

 as shown by the digestion experiments, and the abundant appearance 

 of the pigment in the feces. The failure of the xanthophylls to 

 appear to any extent in the cow's system may be due similarly to the 

 fact that they are apparently more easily destroyed 1 during digestion. 

 Some of them that escape destruction are undoubtedly taken up by 

 the bile and thus enter the system through the portal circulation. 

 Some oxidation probably takes place in the liver. If fat is present 

 to any extent some of the xanthophylls will evidently be taken up and 



1. Willstatter and Mieg. (Ann. d. Chem. 355, p. 1, 1907), state that 

 xanthophylls are very sensitive toward acids. This would lead one to 

 expect that they would be largely destroyed by the gastric juice. Our 

 results were contradictory in this respect. We found an artificial gastric 

 juice to destroy the xanthophylls but the natural gastric juice from the 

 fourth stomach of a cow apparently had no effect on them. 



