192 BACTERIA, YEASTS, AND MOLDS 



The purpose of sterilization is twofold, (i) It delays 

 the souring of the milk. Milk that has been boiled may 

 keep from souring for several days, whereas without boil- 

 ing it will keep only a few hours. With the poorer fami- 

 lies in cities this is the chief purpose of boiling the milk, 

 since it will not keep more than a few hours without ice, 

 and they have no ice chests where it can be preserved 

 from souring. (2) The destruction of disease germs. Milk 

 is a common means by which certain contagious diseases 

 are distributed through a community. The diseases in 

 question are produced by bacteria in the milk, and boiling 

 destroys them. This is the ground upon which physicians 

 and health boards have in the past few years so widely 

 advocated the boiling of milk that is to be used for drink- 

 ing. Since boiling does destroy practically all the disease 

 germs liable to be in milk, it makes it incapable of dis- 

 tributing contagious diseases. 



There are certain disadvantages in boiling milk. The 

 taste is wholly changed, for boiled milk is quite a different 

 article from raw milk. Most people do not enjoy the 

 taste of boiled milk, and the adoption of sterilizing or 

 boiling will, therefore, greatly reduce the amount of milk 

 used as a food. It might indeed be possible to learn to 

 enjoy the taste of boiled milk. Children brought up on 

 it like it, while they cannot endure the taste of raw milk. 

 A more serious objection to sterilization is that the heating 

 .so changes the nature of the milk that it is less easily 

 digested and assimilated. Boiled or sterilized milk can 

 be digested and assimilated readily enough by persons 

 with strong digestive powers, and many children are satis- 

 factorily brought up on it ; nevertheless it is somewhat 



