306 THE CHEMISTRY OF DAIRYING 



computed that if they were all of the largest size a single drop 

 of milk of average quality would contain not less than four 

 million globules, and that if they were all of the smallest size 

 the number would be not less than one thousand millions. 



The average size of the fat globules varies in the milk of 

 different breeds of cows. The smaller globules predominate 

 in that of the Ayrshires, and the larger ones in that of the 

 Jerseys. It is partly for this reason the milk of Ayrshire cows 



FlG. 26. Fat Globules in Milk ( X 200). 



is preferred for cheese making, and that of the Jerseys for 

 cream raising. 



Milk, as it is drawn from the cow, has, of course, the 

 temperature of the animal's body, and under these conditions 

 the fat is necessarily liquid. It is not at first obvious, however, 

 why it should continue in that state when the milk is cooled 

 to the ordinary temperature of the air, which is considerably 

 lower than the solidifying point of the fat ; why, being liquid, 

 the globules do not coalesce, or why they should do so on 

 churning. 



The explanation of the first of these problems is probably 

 to be found in the minute size of the globules. When liquids, 

 e.g. water, are broken up into an extremely fine state of 



