MILK AND ITS PRODUCTS 35 



We have heard of the countless bacteria in the* air 

 that are too small to be seen, but are always ready to 

 enter vegetables and animal substances, if an oppor- 

 tunity is afforded. When food spoils, it is because 

 millions of these tiny organisms have attacked it. 

 If the housekeeper had been careful enough to prevent 

 them from doing injury, the food would still be fit 

 for use. 



But how can such invisible foes be kept from doing 

 harm? In spite of their small size, many facts in 

 regard to these minute destroyers have been dis- 

 covered. For instance, most of them can do little 

 harm in a temperature of from thirty-two to fifty 

 degrees, while a temperature from one hundred fifty- 

 five to two hundred two degrees, if maintained from 

 fifteen to twenty minutes, readily destroys them. 

 They require a certain amount of moisture, and on 

 this account dried foods are not disturbed by them. 

 They do not thrive in anything that is highly spiced, 

 sugared, or mixed with salt, and this is the reason that 

 materials are canned, preserved, or salted. 



Few foods are so easily destroyed by bacteria as 

 milk. What care should be taken to keep this useful 

 food at its best? Both stable and cows should be 

 kept as clean as possible, and the milker should wash 

 his hands and the cow's udder before commencing to 

 milk. As soon as the pail is filled, the milk should 

 be strained, not in the stable, but in a cool room ad- 

 joining, after which it should be poured over a cooling 



