COMPOSITION OF MILK 13 



placed side by side, to make a row an inch long. 

 It has been estimated that a single drop of milk 

 may contain as many as 150,000,000 of fat globules. 

 Jn order to count them, a definite quantity of milk 

 is diluted and drawn into a very fine glass tube and 

 examined under a microscope. 



Relative size of globules. The size of fat glob- 

 ules varies with different breeds and with different 

 individuals in the same breed. The globules be- 

 come smaller as the period of lactation advances. 

 Generally speaking, Jersey and Guernsey milk has 

 the larger fat globules, while the Ayrshire and 

 Holstein milk has the smaller globules. The New 

 York Experiment Station at Geneva reports the 

 following observations on the average size of the 

 fat globules in the fraction of an inch : 



Holstein. 

 Ayrshire. 

 Devon. . . 

 Guernsey, 

 Jersey.... 



10370 



i 

 9350 



i 



9630 



The larger globules in Jersey milk may be five or 

 six times as large as the smaller ones. With most 

 cows the globules are smaller late in the period of 

 lactation. 



Butter fat. Butter fat is composed of several 

 distinct fats with different characteristics. Some 

 are volatile, i. e., may be driven off in vapor; others 



