392 



ELEMENTARY BIOLOGY 



When we consider that the contamination of wells, rivers, and lakes 

 with the germs of disease can be brought about only by discharges 

 from diseased persons (or at least of persons carrying the germs), we 

 see how closely connected are the problems of sewage and health. 



30 r 



1890 



1895 1900 1905 1910 



FIG. 203. Typhoid and water supply 



1015 



For twenty years the deaths from typhoid fever fluctuated between 18 and 31 per 100,000 



of the population. Since 1907, when the state authorities (New York) took charge of water 



regulation, the death rate from this disease has steadily declined 



Wherever there is a sewage system, the law should require that every 

 house be properly connected with the sewer. There is unmistakable 

 evidence that the general health is better among people who use 

 modern water closets than among those who do not. It is also 

 certain that the latter are too frequently sources of danger to others 

 in that the contaminations work their way through the ground into 

 the water supplies upon which others are dependent. Thus again we 



