22 BUTTKR-MAKINO AND C'OMPOSITKJN OF MILK 



Coloring-matter.- It is not kncjwn of what the coloring- 

 matter in milk consists. A substance named lactochrome has 

 been found in milk. S(j far as known, this coloring-substance is 

 closely associated with the fat called palmitin. The amount of 

 coloring-matter varies during the different seasons of the year. 

 It also varies according to the different breeds. During the 

 spring of the year, when cows are first put on grass, the color of 

 of the butter-fat is always higher than it is during the latter por- 

 tion of the summer. During the winter, the fat in milk is quite 

 pale. By feeding the cows some succulent feed in the winter, 

 such as silage, carrots, and beets, the color of the butter-fat is 

 rendered much higher. 



From this it would seem that the change in the color of the 

 fat with the different seasons, and with the food given, is closely 

 associated with chlorophyl, the coloring-matter of grass. 



Other Constituents of Milk. — It is said that constituents 

 such as citric acid, urea, nuclein, lecithin, and galactase are 

 present. Babcock maintains that he has discovered a sub- 

 stance named fibrin. This seems to be similar to the nuclein 

 mentioned by Fleischmann, if not the same. But as these 

 substances are present to a very small extent, citric acid, urea, 

 and fibrin being present to the extent of .12, .007, and .0002 

 per cent respecti\'ely (Fleischmann and Babcock), they are of 

 little importance. 



