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the various districts supplied, some districts of large
areas and several large institutions!, as already stated,
even escaping altogether. Admitting then, the factor of
the infected farm G, it may be stated that the
other factor, working through the distributors, who were
"carriers," showed itself in a special localisation of cases
in certain very small areas, e.g., separate roads. That
both factors were at work, in some areas, there can be
little doubt, and the details of the outbreak are, consequently,
of interest epidemiologically and otherwise. It
is true that the "carrier" infection takes a secondary and
subordinate place in the causes of the outbreak, but, for
a complete understanding of the whole of the details, it
must be considered and allowed for. Idiosyncracy and
susceptibility of patients, too, may have played their parts.
The dates of onsets of the attacks in the notified
patients, set out in Table I., are interesting in connection
with both the farm infection (commencing about the last
week in. November) and the "carrier" infection (commencing
about the same time). These infections continued
at work until the third week in December, when (they
ceased—the cessation tallying with (1) the pasteurisation
of all farm milk before distribution, and (2) the stopping
of the suspected distributors from work. The pasteurisation
of the milk commenced on December 12th, and the
stopping of the suspected distributors at a later date, i.e.,
when the bacteriological evidence proved definitely that
the distributors were, or had recently, been, "carriers"
(actual or probable) of diphtheria.
From December 12th, 1913, onwards, all milk was
pasteurised before being distributed from dairy X,
and all cases of diphtheria connected with that milk,
consequently ceased. What applied to diphtheria should
have applied to other infectious diseases, and it is interesting,
in passing, to note the following details, collected
in the Lambeth area, Norwood Ward, during the month
of January, 1914:—
I 2