44 CANADIAN DAIRYING. 



FORM IN MILK. 



The fat 'and a portion of the casein are held 

 in suspension, and the remainder of the solids are 

 dissolved in the water. The fat is in the form 

 of tiny globules, which vary in size. Guernsey and 

 Jersey cows give milk containing large-sized fat 

 globules, while Ayrshires and Holsteins give milk 

 with small fat globules. The size of the fat globules 

 decreases with a diminished flow of milk, and the 

 number increases. Whether these globules are sur- 

 rounded with a membrane or not has been the subject 

 of considerable controversy, but the question has 

 little practical significance. The chief milk fats are 

 olein (soft), palmitin and stearin (hard), and butyrin 

 (volatile). 



SOURCES OF CONSTITUENTS. 



The sources of the different milk constituents are 

 probably somewhat as follows : 



The water is derived from the food and drink of 

 the cow by transudation from the blood, hence the 

 importance of clean food and pure water for the cow. 



The fat comes from the albuminous portions of the 

 food, and also in all probability, to some extent at 

 least, from the carbohydrates and fat of the food. 



The casein, albumen, and sugar of the milk are 

 probably derived from the nitrogenous parts of the 

 food, through a special cell activity. 



The ash or mineral matter comes partly from the 

 mineral matter in the food by transudation, and 

 partly as a result of cell activity in the gland. 



