138 THE HOUSE FLY—DISEASE CARRIER 
Influence of Flies in the Carriage of Typhoid in Cities 
Much of what we have just written refers to the 
carriage of typhoid by flies in encampments of troops 
and, in such facts as we have given about the Spanish- 
American War and the Boer War, to their effective 
carriage in temporary camps. We have equally shown 
their influence, however, at more or less permanent 
army posts and the certainty of the inference under 
these conditions is acknowledged by practically every 
one. And the same free acknowledgment must be 
made in the case of any emergency which calls together 
for temporary purposes large bodies of men, engaged 
on great public works, for example, as the Panama 
Canal or the construction of great reservoirs, or in 
mining camps. Any slight lack of care in the disposal 
of excreta under such conditions almost invariably 
brings about an outbreak of typhoid, and most often 
by the carriage of the causative organism by flies. But 
does the same thing hold for cities? The opinion of 
a certain class of conservative medical men on this 
point is well expressed in a recent editorial in the Jour¬ 
nal of the American Medical Association, as follows: 
“It is sometimes easier to implant a new idea in the 
human mind than to extract it or modify it when it 
has once taken firm root. The notion that bad smells 
from faulty sewers give rise to specific infections, such 
as diphtheria and typhoid fever, or that piles of gar¬ 
bage ‘breed disease,’ are cases in point. In the public 
mind, methods of garbage disposal and elaborate 
