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38
There are possibly then, at least two factors accounting
tor the local increased incidence of these diseases, viz.:—
The altered age distribution and the growth of the population,
the latter in its effect being divisible into the addition of a
new population in spatial relation to the stable portion and
further, the rate of growth.
This table shows the incidence of each of the diseases
divided out into the quarters of the years, the heavy horizontal
line representing a period of growth of that building section.
The table is an attempt to elucidate how soon or otherwise
local influences came into play in the causation of the disease
The single concrete point shown is that there is a period in
practically all 'cases, of at least six months from the time
the first of the houses are handed over on that Section before
any cases arise. One suggested explanation is that of school
influence; that most children are here that length of time before
being admitted to school, and thereafter school influences act.
In support of this too, is the fact that in the early development
of the Estate, schools were not available for the children for
much longer periods than in the later development. Against
this though are the figures showing the small influence the
modern schools have in the dissemination of infection.
As bearing on the points previously raised, a comparison
of sections 1 and 8 is of interest. No. 1 is a more widely
spread section, the total development of which took over three
years. No. 8 is a much more populated compact section completed
in 18 months. In No. 1, exccpt in the third quarter
of 1922, 'which was the school outbreak of Diphtheria, there
are few leases of either disease until after 1926. In No. 8.
however, after the first period of six months, cases of both
diseases were common.