382 MAN'S IMPROVEMENT OF HIS ENVIRONMENT 



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A diagram to show how typhoid may be spread in a city through an infected milk 

 supply. The black spots in the blocks mean cases of typhoid. A, a farm 

 where typhoid exists ; the dashes in the streets represent the milk route. B is 

 a second farm which sends part of its milk to A ; the milk cans from B are 

 washed at farm A and sent back to B. A few cases of typhoid appear along 

 B's milk route. How do you account for that ? 



may be roughly placed in three different classes. The best milk, 

 coming from farms where the highest sanitary standards exist, 

 where the cows are all tubercular tested, where modern appliances 

 for handling and cooling the milk exist, is known as certified or, in 

 New York City, grade A milk. Most of the milk sold, however, 

 is not so pure nor is so much care taken in handling it. Such milk, 

 known in New York as grade B milk, is pasteurized before de- 

 livery, and is sold only in bottles. A still lower grade of milk 

 (dipped milk) is sold direct from cans. It is evident that such 

 milk, often exposed to dust and other dirt, is unfit for any purpose 

 except for cooking. It should under no circumstances be used for 

 children. A regulation recently made by the New York City 



