30 
In view of the present incomplete knowledge of the subjects of 
both seed and soil in the etiology of typhoid fever it is not possible 
to state positively which is the more concerned in the increased 
summer incidence of the disease. 
FLIES. 
The part played by flies in the transmission of t 3 y)hoid-fever infec- 
tion has been a subject of much discussion in recent years, particularly 
since the publication of the report of the army commission.® 
Among the many suggested explanations of the t}^hoid fever in 
Washington, flies have been presented as being perhaps one of the 
major factors in the spread of the disease. Beheving that, if this 
were so, the seasonal abundance of flies should show a relation to the 
seasonal prevalence of typhoid fever, we, at the beginning of our work 
in 1908, requested Prof. L. O. Howard, chief of the Bureau of Ento- 
mology, Department of Agriculture, to have made a study of the flies 
so that their abundance could be correlated in curves with the 
prevalence of t^’phoid fever. 
The folio vdng excerpt of a letter from Professor Howard to us out- 
hnes the method followed in making the study: 
Our collections were started on June 19 and closed on October 19, 1908. Members 
of tbe Bureau of Entomology were supplied with sheets of fly paper, with instructions 
to expose a double sheet every other day, except Sunday, for a period of 48 hours. 
The sheets were then returned to the bureau and the flies carefully counted and 
recorded, together with such data as could be secured concerning conditions of near-by 
stables and mamu’e dumps. Certain parts of the city among the slums and along the 
water front were not reached by members of the bureau just mentioned. Therefore, 
two assistants were especially employed and made regular rounds on bicycles, fur- 
nished for the purpose, collecting fly-laden sheets and distributing fresh fly paper 
three times a week at a large number of stations selected so as to supplement the 
stations already established by regular employees of the bureau, and thus to cover 
practically the whole city within the city limits. Absence of the Sunday records 
was allowed for where exposure was made in residences by recording only two-thirds 
of the Monday morning catch. In the case of fly papers exposed in meat shops and 
restaurants it was found that flies were usually so plentiful that the maximum catching 
capacity of the paper was reached in 48 hours. In all, sixty-two stations were located 
throughout the city during the progress of the experiment. But, on summing up the 
records, it was found that only twenty-three stations were sufficiently continuous to 
be of value in tabulating the results. Of these, there were eight in the northwest, 
flve in the southwest, six in the southeast, and four in the northeast. 
Charts Nos. 5 and 6 were prepared and furnished us by Professor 
Howard. Chart No. 5 shows the abundance of flies ascertained for 
the different sections of Washington. Chart No. 6 shows the relation 
seasonally of the abundance of flies to the prevalence of typhoid fever. 
« Reed, Walter, Vaughan, Victor C., and Shakespeare, E. 0.: Report on the origin 
and spread of typhoid fever in the E. S. military camps during the Spanish war of 
1898. Washington, Govt. Printing Office, 1904. Vol. 1, 721 p.; Vol. 2, charts. 
