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109
[1897
The cases at the pre-school age fluctuated considerably from the
mean from the beginning of the year up to the first week in June, having
been on eleven occasions above it, and on a similar number of occasions
below it. Thence to the middle of September they were with three
exceptions below it, and it was not until the end of that month
that they began to be stable, and then they showed their greatest
maximum. On the other hand at the post school age the cases were
with two exceptions below the mean line up to the third week in July,
from which period, with one exception, to the third week of December,
they were above it. It will be particularly noticed that in August they
were always above the mean, although irregularly so.
Now the cases at the School Age were almost, without exception,
below the weekly mean during each week of the first four months of the
year, from which period until the end of July there was a strong tendency
to increase, so that the curve instead of being almost constantly below
the mean was no less than five time} above it. This effort to rise was,
however, cut short in the first week in August, from which time to the end
of the first week in September it was below the mean line; and thence
to the end of the year, it was, with the exception of two weeks
constantly above it. This is well seen by the strongly marked notch
on the accompanying chart.
It is remarkable that the disease did not increase until the first
week in September was over, a fact which may be understood if allowance
is made for the period which it requires for incubation. It
could not be expected that the disease would show itself until a
sufficient time had elapsed for it to follow its natural and usual course,
and as from 2 to 7 days is the acknowledged period of incubation it was
to be anticipated if the Schools were really a means of spreading
diphtheria that it would show itself among the scholars as soon as this
period had expired. It has done so, and consequently it seems most
reasonable to conclude that Schools are a very considerable factor in its
propagation.
For this reason, then, it behoves all the teachers of the elementary
schools to be most careful to exclude scholars about whom there is the
least suspicion of a throat ailment, as well as scholars who come from