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



a comparatively large amount of serum with ether and subsequent 

 saponification of the fat thus extracted to really demonstrate the pres- 

 ence of xanthophylls. It is a well-known physiological fact that the 

 proportion of fat in blood serum is comparatively small.* When 

 coupled with the above observations, this seems to indicate a relation 

 between the xanthophylls and the fat carried by the blood. Some 

 observations which will be reported later, in connection with the 

 fate of the carotin and xanthophylls during digestion, will furnish 

 more evidence in this same direction. 



PHYSIOLOGICAL RELATION BETWEEN CAROTIN OF BLOOD SERUM 



AND FOOD OF COW. 



After establishing the chemical relation between the principal 

 blood serum lipochrome and the carotin of the food, it became im- 

 portant to establish a similar relation from a physiological standpoint. 

 Very fortunately this was recognized previous to conducting some of 

 the important feeding experiments which showed the relation between 

 the color of milk fat and the food of the cow, and which were re- 

 ported in Research Bulletin No. io/ Missouri Agr. Exp. Sta., the 

 second bulletin in this series. It was accordingly arranged to study 

 the variation in the amount of carotin and xanthophylls in the blood 

 serum during portions of these feeding experiments. In this way it 

 could be determined what relation exists between the amount of carotin 

 and xanthophylls in the blood serum and the amount of these pigments 

 in the milk fat, as well as the relation between the amount of carotin 

 and xanthophylls in the serum and amount of these pigments in 

 the food. Such a study required the devising of some method of 

 analysis whereby the color of the various blood serums could be com- 

 pared with each other and also with the color of the butter fat. 

 The following method was adopted. 



In the case of live cows whose blood was to be tested, a trocar 

 was inserted in the jugular vein and 200 to 250 c. cm. of blood drawn 

 off into a glass cylinder. As soon as the blood had clotted and suf- 

 ficient serum had pressed out, two 10 cc. portions were pipetted off 

 and carefully dessicated with an excess of plaster of Paris. The 

 powdered mass was moistened with absolute alcohol, and the color 

 extracted immediately by shaking with the selected solvent until color- 

 less. For one sample the solvent was ether and for the other sample 

 the solvent was petroleum ether. In all the studies the petroleum 



*Nate: Hammerstein gives .1 to .7%. 



1. Also Jour. Biol. Chem. 17, p. 19! (1914). 



