WATER SUPPLY 303 



used in the last-named city is said to come from eight states and 

 from Canada. During shipment it must be kept in refrigerator 

 cars, and during transit to customers it should be iced. Why? 

 All but the highest grade milk should be pasteurized. Why? 

 Milk should be bottled by machinery, if possible, to insure no 

 personal contact ; it should be kept in clean, cool places ; and no 

 milk except that which is to be used for cooking should be sold 

 by dipping from cans. Why is this method of dispensing milk 

 likely to make it impure ? 



Care of Milk in the Home. — Finally, milk at home should re- 

 ceive the best of care. It should be kept on ice and in covered 

 bottles, because it readily takes up the odors of other foods. If 

 we are not certain of its purity or keeping qualities, it should be 

 pasteurized at home. Why? 



Water Supplies. — One of the greatest assets to the health of a 

 large city is pure water. By pure water we mean water free from 

 all organic impuritieS; including germs. Water from springs and 

 deep driven wells is the safest water ; that from large reservoirs 

 next best ; while water that has drainage in it, river water for 

 example, is very unsafe unless properly treated. 



The water from deep wells or springs, if properly protected, will 

 contain few bacteria. Water taken from shallow, unprotected 

 wells has from 100 to 20,000 bacteria per cubic centimeter. Water 

 taken from protected streams into which no sewage flows has but 

 few bacteria (from 50 to 300 bacteria per cubic centimeter), and 

 these are destroyed if exposed to the action of the sun and the con- 

 stant aeration (mixing with oxygen) which the surface water 

 receives in a large lake or reservoir. But water taken from a river 

 into which the sewage of towns and cities flows may contain many 

 hundreds of thousands of bacteria to the cubic centimeter, and 

 must be filtered and chlorinated before it is fit for use. 



Typhoid fever germs live in the intestine, hence the excreta of 

 a typhoid patient contain large numbers of typhoid germs. In a 

 city such germs might eventually pass from the sewer into a river 

 or a lake. Many cities take their w^ater supply directly from 

 rivers, sometimes not far below another large town. Such cities 

 must take many germs into their water supply. Many cities, as 

 Cleveland and Buffalo, take their water from lakes into which 



