428 A YEAR IN SCIENCE 



its breeding places. Swamps and ditches must be 

 drained; rain barrels, open wells or any receptacles 

 holding water should be carefully screened. The 

 wrigglers can be destroyed by a film of oil on the water. 

 This enters the breathing pores and readily kills the 

 larvae. 



Yellow fever has practically been stamped out of 

 New Orleans by these measures. Some of the earlier 

 attempts to dig the Panama Canal were futile because 

 of the prevalence of yellow fever. When operations 

 were finally begun by our government, one of the first 

 things which it did was to rid the region of the yellow 

 fever mosquito. 



Milk. Milk is very easily contaminated with germs. 

 Many children's diseases, typhoid fever, and tuber- 

 culosis, are spread by infected milk. Consequently 

 the death rate for babies and young children is very 

 great. Every care possible should be taken to see 

 that the milk which they use is free from germs. In 

 summer the milk must be kept cool to prevent its 

 "spoiling," and the bottles used for feeding the babies 

 must also be sterilized. 



Water. The source of drinking water in large cities 

 is very frequently from rivers or lakes. This makes it 

 very liable to contamination from sewage, and sewage 

 is almost certain to contain germs of typhoid and other 

 diseases. City water should be frequently examined to 

 see that it contains no germs. If it is known to be bad, 

 or even suspected, it is wise to boil the water before 



