366 HUMAN BIOLOGY 



highway, and automobile transportation between home and 

 school. 



While the aesthetic and economic dangers of a city 

 atmosphere polluted by smoke, dusts, industrial gases, 

 fumes and odors is easily determined and measured, it is a 

 matter of great difficulty to prove that the fouHng of the 

 air in cities is the direct or contributing cause of important 

 groups of sicknesses and deaths. 



Where evergreen trees, vines, shrubs and the sturdy 

 grasses and flowering plants cannot survive the deposit of 

 tar, ash, sulphur and the hmitation of sunhght even in the 

 open yards and park spaces of cities, we may assume that 

 the area is not fit for the human child. City environment as 

 sketched here is common in many American cities. In all 

 such city quarters we find the poorest paid, least intelhgent or 

 certainly the most underprivileged of our unskilled laboring 

 population and the high sickness and death rates. It is 

 impossible to be sure what part of the poor hygiene is 

 properly chargeable to the bad city-made physical environ- 

 ment and what is the share of ignorance, poverty, foreign 

 birth and unstable economic status. 



WATER SUPPLIES 



From the point of view of our present study, water 

 represents one of the essential contacts between man and 

 his environment. It extends the range of the environment 

 and makes it possible for an adverse condition, such as a 

 typhoid case or carrier, at some rural point, to affect the 

 individual or a large part of the population in a distant 

 city community. The prime essential in a domestic water 

 supply is freedom from pathogenic bacteria, and this 

 in general means freedom from human pollution. Typhoid 

 fever is the disease, in this country at least, most frequently 

 associated with polluted water and the typhoid fever 

 statistics of cities before and after they have undertaken 

 the purification of an impure water supply furnish clear 

 evidence of this association. In the city of Pittsburgh, for 

 example, filtration was begun in 1908, although portions 

 of the city continued to drink unfiltered river water for the 

 next two years. The typhoid fever death rate for the period 



