6o George C. Whipple 



at the International Engineering Congress at St. Louis, called atten- 

 tion to this same fact, that after the change from an impure to a pure 

 supply of water the general death-rate of certain communities investi- 

 gated fell by an amount considerably greater than that resulting from 

 typhoid fever alone — indicating either that certain other infectious 

 diseases were reduced more than typhoid fever, or that the general 

 health tone of the community had been improved. Thus, for five 

 cities where the water supply had been radically improved he found : 



Per icx3,ooo 

 Reduction in total death-rate in five cities with the introduction of a pure water 



supply 440 



Normal reduction due to general improved sanitary conditions, computed from 



average of cities similarly situated, but with no radical change in water supply 137 



Difference, being decrease in death-rate attributable to change in water supply . 303 

 Of this, the reduction in deaths from typhoid fever was 71 



Leaving deaths from other causes attributable to change in water supply . . . 232 



From these facts it is evident that to place the financial loss to a 

 community as $6,000 for each death from typhoid fever due to the 

 public water supply is to use too low a figure. It probably ought to be 

 several times as high ; but recognizing the lower financial value placed 

 on the lives of infants, and the less serious character of the other dis- 

 eases, and wishing to be as conservative as possible, for the reason 

 that typhoid fever is not entirely a water-borne disease, $10,000 per 

 typhoid death has been used in the calculation which follows. 



Since typhoid fever is a disease which may be transmitted in other 

 ways than by the water (as, for instance, by milk, shell-fish, or flies), it 

 is necessary to allow a certain death-rate for these other causes, for 

 even in a city where the water supply is perfect there may still be some 

 typhoid fever. To establish this "normal"* is a difficult matter, but 

 for purposes of calculation we may assume it to be determined and 

 represent it by the letter N. 



If we assume that all typhoid fever in excess of N is due to the 

 water supply, and if we assume that the daily consumption of water is 

 100 gallons per capita, then letting T equal the typhoid fever death- 

 rate per 100,000 — 



(T—N) 10,000 = loss to the community in dollars for 365 X 100 X 



11 r ^ T> {T-N)i,ooo 

 100,000 gallons of water, or D= 7 ■ =2.75(7 —A'), 



♦This term "normal" must not be assumed to mean necessary typhoid. 



