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64
DIPHTHERIA.
280 cases of diphtheria were notified during the year, giving
an incidence.rate of just under 2 per 1,000, a rate practically
identical with the rate of last year, and below the mean for the
period during which the disease has been notifiable. Up to 1902
the incidence of diphtheria in Willesden was progressive, but
since then there has been a marked fall in the number of cases
notified.
The greatest incidence is still in the western part of the
district, and more particularly in the Church End Ward.
In the chart on page 56 are spotted the cases of diphtheria
occurring in Willesden during the five years 1901-1905.
They have been distributed equally among the houses in the
streets in which they have occurred. The chart very clearly
shows how heavy is the incidence of this disease in the lower
lying parts of the Brent area.
In my evidence at a Local Government Board enquiry into
the value of the intercepting trap, I pointed out how this incidence
was much greater on houses provided with interceptors than on
the older houses where the drains were not disconnected from the
sewers. I also showed that in the lower lying parts of the district
drains with interceptors were more liable to blockage or to
provide ventilation to the sewers beneath the windows of the
houses where the cap of the raking arm had been displaced. The
frequency with which this is found to happen is shown in
Table No. 27, based on special systematic inspections of manholes
throughout the district. I suggested, and I still think, that
a causal relationship exists between exposure of young children
to the emanations of sewage and the incidence of diphtheria;
and I state as a fact that the intercepting trap and the drain