356 BIOLOGY AND HUMAN LIFE 



inconsiderate customers. They have regulations as to the refrig- 

 eration of meats and fresh fish, the management of kitchens for 

 hotels and restaurants, the handling of food served in public 

 places, the conduct of bakeries and refreshment parlors, and 

 so on. The most elaborate regulations have been adopted in 

 regard to milk, since milk is the most easily spoiled of all our 

 foods, and since it is at the same time so indispensable to many 

 people, especially children and infants and the sick. 



270. Milk. While the milk in the udder of the cow may be 

 quite free of any contamination, by the time the milk has been 

 poured from the pail to the can it is sure to have many bacteria 

 floating in it. The high temperature of the milk fresh from the 

 cow makes the multiplication of the organisms proceed very 

 rapidly. By the time the milk is ready for delivery in the city 

 it contains a large number of bacteria in every drop. On page 

 355 are given the rules for the care of milk intended for city 

 markets. There is a biological reason for every rule given, and 

 the reason should be clear to the student in every case. It has 

 been found practically impossible to obtain milk in large quan- 

 tities without excessive numbers of bacteria. For this reason 

 the practice of pasteurization has come into more and more gen- 

 eral use. This consists in raising the temperature of the milk to 

 about i40°-i55° F. and keeping it there for from ten to twenty 

 minutes. Pasteurization does not, of course, remove the bac- 

 teria ; it only kills them. Where it is impossible to get certified 

 milk it is worth while to pasteurize the milk at home, using a 

 steam cooker or a double boiler (see Fig. 165). 



Preservatives should never be used in milk, since the only 

 kinds that would not show themselves by taste or odor are apt 

 to be injurious. 



271. Official recognition of microbes. In every progressive 

 community the danger to health and life that lies in various 

 invisible microbes is officially recognized in public regulations 

 and government activities. We are protected from these dangers 

 even where we are ignorant of their existence, and even where 

 we ^^ don't believe in microbes." A mere enumeration of the 



