138 
IOWA ACADEMY OF SCIENCE 
“The risks in sanitation that will remain from the presence of 
the railroad after the prescribed safeguards are rigorously pro- 
vided, will, I believe, be of the microscopic and academic character 
that we continually have to accept; indeed, it can be figured out 
that the chance of pollution from the railroad after providing rea- 
sonable safeguards, will not be one-tenth as great as from other 
sources of possible pollution in lumber camps, sawmill settlements, 
strollers along the stream and in the branch railroad, all of which 
exist today and some of which will continue to exist indefinitely, 
and which, taken all together, are, after all, small in proportion to 
those that are found along the water supplies of many cities with- 
out serious epidemics. 
“Those fond of figures may be interested in the following com- 
putation : 
“Suppose 1,000 different passengers per day to pass through 
the Cedar River watershed on the St. Paul road; this is 365,000 
per year. Health statistics of Massachusetts (the most complete 
in the United States) show 1.24 cases of typhoid per 1,000 inhab- 
itants per year. Convalescents and those who have the disease 
in a mild form, in the first week or two of the disease may travel. 
We can at most assume that 450 out of all these 365,000 passengers 
would have typhoid at some time during the year. Calling the 
duration of those stages of the disease within which one could 
travel, a month, or one-twelfth of a year, we can expect only 
thirty-seven persons actually in the infectious stages will travel 
over the road during the year. 
“If these have so many as four stools per day, the chance is that 
in the twenty minutes (or one-seventy-second of a day) occupied 
by ordinary trains passing through the watershed, these thirty- 
seven cases would produce : Thirty-seven cases multiplied by four 
stools, divided by seventy-two, equals two stools per year on track ; 
or the probability is that only two discharges per year of excreta 
from typhoid patients are likely to be dropped on this entire ten 
miles of roadbed from passengers. 
“When we consider that one of the residents of a lumber camp 
sick with typhoid may have an average of say two stools per day 
(we have figured twice this for the passengers), or say at least 
fifty stools during his entire illness — this is twenty-five times as 
many as we figure out as likely to come from all the passengers in 
a year. 
“With 500 persons resident in the watershed, the probability is. 
