CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 



423 



ether extract proved to be the easiest to handle as it was practically 

 free from water. The extract in each case was carefully evaporated 

 to a volume of i to 2 cubic centimeters and then made up to 12^/2 

 cubic centimeters with absolute alcohol, this volume being just suf- 

 ficient to fill the one-inch cell of the Lovibond Tintometer. The 

 solutions were analyzed at once in the Tintometer and their color 

 readings recorded. Duplicate determinations were thus obtained. 

 This was considered necessary since the method was not free from 

 error due to possible bleaching of the extracted pigments. The entire 

 procedure was carried out as quickly as possible. The results of the 

 duplicate determinations were averaged. 



The first series of observations of the color of the milk fat and 

 blood serum corresponding to various pigmented rations was made 

 with Ayrshire cow No. 301. These feeding experiments and the result- 

 ing variation in the color of the milk fat were shown in detail in 

 Tables 12, 13 and 14 of the preceding bulletin dealing with the milk 

 fat pigment. The relation between the character of the ration, and 

 the color of the milk fat and blood serum at stated intervals during 

 the feeding experiments is shown in Table No. 3, below. 



TABLE No. 3. THE RELATION OF THE CHARACTER OF THE RATION TO THE COLOR 



OF THE MILK FAT AND BLOOD SERUM. 



AYRSHIRE Cow No. 301. 



