442 BIOLOGY FOR BEGINNERS 



covering in some cases over sixty items that tend toward supply- 

 ing clean milk to the dealer in the city. 



The dealer is again subject to equally careful control. He must 

 not let the milk get warmer than fifty degrees, he must provide 

 clean cans and handling conditions, he must sell in sealed and 

 labeled bottles, and his milk must be subject to examination for 

 bacteria, at any time. If any of these conditions are found danger- 

 ous, the milk is destroyed. 



Milk normally contains bacteria, mostly harmless and some 

 useful, but the total must not exceed 100,000 per cubic centimeter 

 which is not very numerous for bacteria, though well-handled 

 milk ought to be kept far below this limit. Milk must have at 

 least 3.25 per cent of butter fat and must not contain any pre- 

 servatives, such as borax, soda, or formaldehyde. 



Sanitation. Regulations as to sewage and garbage disposal are 

 in force in most cities, and means are provided at public expense 

 for the sanitary disposal of all wastes. Stables and outhouses are 

 either forbidden or restricted. Factories are not permitted to 

 pollute the air or water with their waste products. 



Streets are drained, sprinkled, oiled, paved, and flushed with 

 water to remove dirt and to prevent dust. Trees and parks are 

 provided to improve the air and give places for outdoor rest to the 

 population. 



Disease Prevention. It is in this department that modern hy- 

 giene has made its greatest progress. We now provide free hos- 

 pitals, clinics, and dispensaries where the sick may receive treat- 

 ment. We have visiting nurses, city physicians, and school health 

 'examinations to make sure that all who need help, shall receive it. 

 Stringent laws regulate vaccination, quarantine, and disinfection 

 of infected premises. Coughing, sneezing, and spitting are for- 

 bidden where they endanger the public health, and the public 

 towel and drinking cup are, fortunately, things of the past. 



Campaigns of education by printed matter, pictures, school in- 

 struction and lectures, have been undertaken by city, state, and 

 national governments, as well as by life insurance companies and 

 institutions like the Rockefeller Foundation. 



