FARM ANIMALS 



389 



fresh for several days because there are so few bacteria 

 (see page 261). Milk for babies in sometimes kept fresh 

 by heating to 155 F. for twenty minutes, and then 

 cooling it. This is called pasteurizing (see page 261). 

 When milk is left quiet, even for a short time, we find 

 cream gathering on the top, because the butter-fat it 

 contains is lighter than water. This cream we may 

 after a while skim off for table use, or gather it till we 

 have enough for a churning into butter and buttermilk. 

 Or we may leave cream and all for a couple of days 

 to sour, and make clabber. This is much liked by 

 many people, and is a very healthful food, as also is 

 buttermilk. 



But in creameries, where hundreds and even thousands 

 of gallons of milk must be handled ^^^ 



every day, we cannot wait for the cream 

 to rise. The milk is there run into the 

 bowl of a machine called a separator. 

 As this bowl is made to turn rapidly, 

 we find the cream gathering in its 

 middle, while skim milk goes to the 

 outside. Two pipes are put in in such 

 a way that the cream runs out of one, 

 the skim milk out of the other, and so 

 in a very short time large quantities of 

 milk can be much more thoroughly 

 skimmed than can be done by setting 

 in pans. Then the cream is set aside to ripen for churning, 

 while the skim milk is fed to pigs or made into a kind of 

 cheese. 



FIG. 198. Separator. 



