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29
The weekly average number of notifications at all
ages was determined, and a curve constructed, showing
the percentage variation from that mean for
each week of the year. It was found that there was
in that part of the curve relating to the month of
August, a well-defined depression, extending from the
32nd to the 35th week. That depression occurred in
the middle of a rise in the curve for the series
of weeks. A similar, but less marked depression was
noted in the corresponding curve for 1892. For the
purpose of closer examination of the curve of 1893,
the cases of scarlet fever were divided into three
groups: (a) those occurring in children from 0-3
years of age, i.e., "those too young to attend school
(b) those in children aged from 3-13 years of age, i.e.,
"those at the school-age period of life"; and (c)
those of individuals aged 13 years and upwards, i.e.,
"those who have, in great part, left school." He
goes on to say:
"If curves be constructed with the cases included in
these three groups, it will be seen that the August
depression is much accentuated in the curve relating to
children from 3-13 years of age, and that the depression in
the curve relating to infants from 0-3 years occurs a little
later. This striking diminution of scarlet fever in the
month of August, occurring especially among children at
the school-age period of life, necessarily raises the
question whether disease had been spreading in schools,
and whether the summer holiday has arrested the spread
of disease due to this cause.
"At this season of the year there is, however, another
condition which deserves consideration. Coincident with