668 SEDGWICK AND WINSLOW. BACILLUS OF TYPHOID FEVER. 
o 
contagious iriiittTKil being diirerent in each individual instance. For this sort of 
infection \Yhich spreads gradually in a community instead of striking a larije number 
of persons at a single blow, the term "prosodcmic," meaning "throuf'-h" or "amon<'-" 
the people^ has been suggested. 
In the examination of data bearing on the question of the seasonal prevalence of 
ty[i}i()i<l fever it is obviously the prosodemic disease which should be mainly considered. 
Casus of this sort furnish a large number of independent facts which may be avera<rcd 
together fairly 
lys be a perturbincj element. Thus, for 
c 
xample, a public water supply furnishes exceptional facilities for the distribution of 
tifection from its watershed to a large number of individuals. Twelve hundred cases 
f typhoid fever at Plymouth, Pa., derived from a sincrle house on the banks of a 
for a study of normal 
fifty 
far less significance than 
of infection are separate and independ 
Curves of seasonal variation which are based on a small number of 
lys be liable t 
loid deaths be 
o 
o 
b 
due to single epidemics; and if our tables of 
once be seen that four of the nine exceptions 
to this cause. Thus the form of the Oak- 
distorted by the epidemic of twenty-two deaths in July, 189 
arc informed by the local authorities was due to an infection of the milk supply. 
The largest number of deaths in any other month in the ten years was seven, so that 
this irregularity could not be compensated. Similarly, the Munich curve owes its 
peculiarity to the epidemic of thirty-five deaths in June and July of 1893, the largest 
nuinber m any other month being nine. The curve for Vienna is controlled, in a 
snmlar way, by an epidemic in December, 1888, and January and February, 1889. In 
all these cases the curve would follow the temperature more or less normally if these 
perturbations were eliminated. Again for Dresden the tot 
small that eight cases in April, 1894, cause a notable distorti 
this city did follow the temperature when there was enoi 
of d 
Th 
We may 
hy Fiedler's figures for 1850-60, quoted 
gh of 
of the Oakland, Munich. Vienna, and 
uresden curves are explainod hy the fact tliat the lu.mber of cases considered .. -- 
smuU to ehmu.a(e the haphazard effect of epidemics. There remain to be explained 
of which 
ptions offered by Chicago, Cincinnati, Newark, Paris, and Philadeli 
i uries tiie amount of material is amply sufficient to prevent mere chance 
irregu anties. If the curves for these five cities be compared, it will at once be noted 
that they exhibit a remarkable resembl 
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