196 BACTERIA, YEASTS, AND MOLDS 



One caution should be given regarding the use of pas- 

 teurized milk : the milk must be used quickly after pas- 

 teurizing. It is true that such milk may keep for two 

 days without difificulty, but bacteria are growing in it all 

 the while, and although the milk does not sour it soon 

 becomes unfit to drink. Hence pasteurized milk must be 

 used quickly, at least within twenty-four hours from the 

 time when it was pasteurized, and meantime it should be 

 kept cool just as if it had not been pasteurized. 



The most important rule in regard to the use of milk 

 in the household is that it should be used fresh. No satis- 

 factory method of keeping it can prevent all bacteria from 

 growing, and although the use of ice and of pasteurization 

 or sterilization may keep it in a drinkable condition for a 

 day, two days, or even longer, it is always suspicious after 

 it has been kept for this length of time. Milk is plenty 

 old enough by the time it reaches the house, and it should 

 therefore always be used fresh. It is far better to obtain 

 it frequently, in small quantities, using it up as soon as 

 possible after it reaches the home. 



Above all it should be emphasized that clean milk is 

 better than pasteurized milk. The proper procedure is to 

 obtain milk in good condition and then pasteurization is 

 unnecessary. Pasteurization is not a guard against filth, 

 but only an unsatisfactory means of destroying the dis- 

 ease germs which may chance to be in the milk from 

 some source of accidental contamination. When young 

 children must be fed upon cow's milk probably the only 

 safe procedure is to adopt home pasteurization or to use 

 concentrated milk, unless one can afford the expense of 

 purchasing high-grade certified milk. 



