Preservation of Milk. 51 



desired temperature. Where large quantities of milk 

 are to be treated, the "continuous flow" machines are 

 used, through which the milk passes in a constant 

 stream. 



Household pasteurization of milk. It is often desir- 

 able to pasteurize the milk to be used in the home, 

 especially that intended for children, and when the 

 milk comes from cows not known to be free from tuber*- 



FIG. 10. A HOME-MADE PASTEURIZER. 

 The tumbler prevents the formation of a membrane 

 on the milk during the heating and also pro- 

 tects the mouth of the bottle from dust. 



culosis. The process can be easily carried out in milk 

 bottles or fruit jars. These should be closed in some 

 way in order to prevent the formation of the "skin" 

 that forms on milk heated in an open vessel. This 

 membrane has a protective influence on the bacteria 

 embedded in it. The bottles are placed in a vessel hav- 

 ing a false bottom to avoid breaking them. The vessel 

 is filled with water to the height of the milk in the 



