FOODS. 151 



Impurities in Water. The great source of danger is 

 from what are called "organic" impurities. Bacteria will 

 not live and grow in pure water. They must have some- 

 thing on which to feed and grow. But in water contain- 

 ing a large amount of decaying animal or vegetable matter 

 they are likely to abound. And the most dangerous 

 sources of contamination are cesspools and sewers. Water 

 may be contaminated by such material and not have bac- 

 teria in it, but is very likely to harbor such foes. 



Contamination from Cesspools. The ordinary cess- 

 pool is a grave source of danger. Because the well may 

 be on higher ground than the cesspool does not give as- 

 surance that the water may not be polluted. Often when 

 the surface of the ground slopes in one direction, the strata 

 underneath may slope in just the opposite direction, and 

 the well may be the reservoir into which the cesspool is 

 drained. 



Good authorities say that a cesspool should not be 

 allowed within a hundred feet of a well. 



Abolish the Cesspool. But it is better and safer to 

 have no cesspool. Where a sewer system is not to be 

 had, it is better to allow no great accumulation of such 

 material. A deep pit in which a quantity of semiliquid 

 matter gathers is not only a nuisance, but a source of 

 danger. Privies should have a very shallow pit, or none, 

 and should be cleaned often. There should be a little 

 dust sprinkled in each day, and occasionally some " chlorid 

 of lime " or sulphate of iron. 



Typhoid Fever. Typhoid fever is now known to be 

 usually caused by drinking water. The dejecta of some 

 one who has had the disease find their way into the source 

 of the drinking water. In many cases this has been clearly 



