SYMPOSIUM ON PUBLIC HEALTH PROBLEMS 96 
system should be regarded as a concomitant part of a sewerage 
system, for the reason that neither of these utilities can be 
properly operated or give satisfactory service without the 
other. 
The prime object and advantage of a sewerage system from 
a sanitary point of view is to quickly, inoffensively and ef- 
fectively remove human wastes, thereby preventing them from 
constituting a nuisance or endangering public health. Not- 
withstanding the fact that the best of engineering ability has 
been devoted to the perfection of sewerage design and construc- 
tion, and that it is now possible to design and build such sys- 
tems that are economical, good in operation, and an absolute 
guarantee against danger to public health, insofar as such 
works can affect the public health, yet in our practices, es- 
pecially in the rural communities and smaller cities, we are 
little further advanced than the most primitive savages. 
Many efforts have been made to show by statistics the ef- 
fect of a sewerage system on public health, but these efforts 
have not generally been successful, because it has not been 
possible to separate the influence of the sewerage system from 
other influences, and moreover it is very rare that full advan- 
tage is taken of the presence of a sewerage system by compel- 
ing the use of the system by all property owners, wherever 
the sewers are available. In many instances, also, the sewer- 
age system is not sufficiently extensive to permit full ad- 
vantage being taken thereof. However, it is possible to observe 
tendencies, even though an exact numerical value cannot be 
placed upon such tendencies, and there seems to be no room 
to doubt that a properly designed and properly operated sewer- 
age system has a very great value in protecting the public 
health. 
On the basis of extensive observations throughout the 
United States, the United States Public Health Service has 
reached the conclusion that in cities where the public water 
supply may be regarded as safe, the installation of a complete 
sewerage system will reduce the typhoid fever death rate in 
northern cities to ten or under, per hundred thousand, and in 
southern cities the reduction will be to twenty or less per hun- 
dred thousand. 
