COMPOSITION AND QUALITIES OF MILK 297 



find out if it is possible to increase the per cent, of fat in a 

 cow*s milk, but they have all failed to do so. The food does 

 influence the quality of the fat, but not the quantity, except 

 as it influences the amount of milk given by the cow. Cotton- 

 seed meal makes the fat globules hard, while oil meal makes 

 them soft. 



As was observed in the table, the specific gravity of milk is 

 greater than that of water; that is, milk is heavier than water. 

 The space which would hold 1,000 pounds of water would 

 hold 1,032 pounds of milk. The sugar in milk gives it a 

 sweet taste. Milk has an odor due to certain volatile oils in 

 it. The yellowish tinge is given to it by the globules of fat. 

 The milk from a fresh cow or one feeding on succulent feed 

 has a more yellowish tinge than the milk from a cow old 

 in milk or one fed on dry feed. Milk from Holstein cows is 

 whiter than that from Jerseys. If fresh milk be tested with 

 red litmus paper it will turn the litmus paper blue, showing 

 an alkaline reaction; but if blue litmus be used it will be 

 turned red, showing the presence of an acid. The acid con- 

 dition is said to come from the casein, while the alkaline 

 condition is the natural state of the rest of the milk. How- 

 ever, if milk stands for a short time, it becomes definitely acid. 



Colostrum. — The milk which a cow gives while a calf is 

 very young is quite different from ordinary milk and is called 

 colostrum. It is especially adapted to the needs of the young 

 calf, but is not at all fit for human food. The colostrum is a 

 sticky, yellow, sweet milk, quite rich in albumen, and has 

 less water than ordinary milk. Milk should not be used for 

 human food until the calf is four days to a week old. It is 

 safe to use fresh milk that does not coagulate when boiled. 

 A purple precipitation in a test-tube after adding a little sul- 



