446 MISSOURI AGRICULTURAL EXP. STA. RESEARCH BULLETIN NO. 12 



enter the blood dissolved in fat. In this connection it is of interest 

 to recall that we have shown 1 that there is evidence to indicate that 

 what xanthophylls can be found in the blood are present dissolved 

 in fat. 



An additional possible explanation of this whole question should 

 not be overlooked, however, namely, that the difference in the pro- 

 portion of carotin and xanthophylls taken up by the cow's body 

 may be due entirely to the difference in chemical composition 

 between carotin and xanthophylls. Carotin is an unsaturated hydro- 

 carbon and is furthermore capable of combining with a protein of the 

 blood, as we have shown. 2 The xanthophylls, on the other hand, are 

 carbon, hydrogen and oxygen compounds, in fact are chemically caro- 

 tin-dioxides. Although still unsaturated bodies, their slight difference 

 in composition from carotin, may prevent their combination with the 

 serum albumin, thus making it impossible for them to appear to any 

 extent in the blood and fatty formations of the cow's body. If fat 

 played a greater part in the food of the cow, the xanthophylls would 

 undoubtedly appear to a greater extent in the body of this animal. 



SUMMARY 



1. Carotin is assimilated from the food of the cow in preference 

 to xanthophylls partly because of its greater stability toward the 

 juices of the digestive tract. Xanthophylls are much more soluble 

 in bile than carotin, 3 which probably accounts for their appearance 

 in the fat of the blood. 



2. It is probable that carotin forms by far the greater part of 

 the lipochromes of the cow's body chiefly on account of its ability 

 to form a compound with one of the proteins of the blood. The 

 xanthophylls, being of different composition, probably are not capable 

 of forming such a compound. 



BIBLIOGRAPHY 



1. Fischer and Rose: Zeit. f. Physiol. Chem. 88, p. 331 (1913). 



2. Palmer and Eckles: Missouri Agricultural Experiment Station 

 Research Bulletins Nos. 10 and n (1914); Jour. Biol. Chem. 

 17, pp. 191, 211, 223 (1914). 



3. Willstatter and Mieg: Ann. d. Chem. 355, p. I (1907). 



1. This Bulletin, page 422; Jour. Biol. Chem. 17, p. 211, 1914. 



2. lUd. 



3. A confirmation of the very slight solubility of carotin in bile is seen 

 in the recent finding of Fischer and Rose (Zeit f. Physiol. Chem. 88, p. 331, 

 1 ! 913), that the gall stones of cows contain crystallizable carotin. No 

 xanthophylls were found. 



