CHAPTER VI. 



COMPOSITION AND PHYSICAL PROPERTIES 

 OF MILK. 



Cow's milk is chiefly used for household and com- 

 mercial purposes in Canada. The flow of milk from 

 other animals is not sufficient to induce the Canadian 

 farmer to make use of it. The cow has responded 

 to man's efforts for large milk production better than 

 any other animal. It has a specific gravity (weight as 

 compared with water) ranging from 1.028 to 1.036, and 

 averages about 1.032, i.e., it is about thirty-two thous- 

 andths heavier than water. This increase in weight 

 is due to the heavier " solids not fat," and not to 

 the fat, which is lighter than water. 



Colostrum milk, or the milk which is first given by 

 the cow after freshening, is a sticky, yellow, sweet 

 fluid, containing a high percentage of albumen, which 

 takes the place of casein in normal milk. It has a 

 high percentage of solids, but the percentage of fat 

 varies considerably with different cows. With some 

 cows the fat content of colostrum milk is high, and 

 with others low. It may vary from two to eight per 

 cent. Colostrum changes to normal milk in from five 

 to twelve days after freshening. The addition of sul- 

 phuric acid to colostrum will cause a purple precipi- 

 tate in the Babcock test-bottle. It should not be 



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