MAN'S IMPROVEMENT OF HIS ENVIRONMENT 381 



be free from bacteria. But immediately on reaching the air it 

 may receive bacteria from the air, from the hands of the person 

 who milks the cows, from the pail, or from the cow herself. Cows 

 should, therefore, be milked in surroundings that are sanitary, 

 the milkers should wear clean garments, put on over their ordinary 

 clothes at milking time, while pails and all utensils used should 

 be kept clean. Especially the surface exposed on the udder from 

 which the milk is drawn should be cleansed before milking. 



Most large cities now send inspectors to the farms from which 

 milk is supplied. Farms that do not accept certain standards of 

 cleanliness are not allowed to have their milk become part of the 

 city supply. 



Tuberculosis and Milk. It is recognized that in some Euro 

 pean countries from 30 to 40 per cent of all cattle have tuberculosis. 

 Many dairy herds in this country are also infected. It is alsc 

 known that the tubercle bacillus of cattle and man are much alike 

 in form and action and that probably the germ from cattle would 

 cause tuberculosis in man. Fortunately, the tuberculosis germ 

 does not grow in milk, so that even if milk from tubercular cattle 

 should get into our supply, it would be diluted with the milk of 

 healthy cattle. In order to protect our milk supply from these 

 germs it would be necessary to kill all tubercular cattle (almost an 

 impossibility) or to pasteurize our milk so as to kill the germs in it. 



Other Disease Germs in Milk. We have already shown 

 how typhoid may be spread through milk. Usually such out 

 breaks may be traced to a single case of typhoid, often a person 

 who is a " typhoid carrier," i.e. one who may not suffer from the 

 effects of the disease, but who carries the germs in his body, spread 

 ing them by contact. A recent epidemic of typhoid in New York 

 City was traced to a single typhoid carrier on a farm far from the 

 city. Sometimes the milk cans may be washed in contaminated 

 water or the cows may even get the germs on their udders by wad 

 ing in a polluted stream. Diphtheria, scarlet fever, and Asiatic 

 cholera are also undoubtedly spread through milk supplies. Milk 

 also plays a very important part in the high death rate from diar- 

 rheal diseases among young children in warm weather. Why? 



Grades of Milk in a City Supply. Milk which comes to a city 



