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(2) No particular incidence on milk drinkers, i.e., no
special milk age- and sex-incidence, children being
specially exempt.
N.B.—The children may have escaped owing to
the custom in better class houses of cooking milk
that is to be consumed by them, or it may be that
they consumed nursery milk from the cows belonging
to dairy X, this nursery milk being unmixed
with the ordinary farm milks.
(3) No sudden outburst of cases.
(4) Notified patients scattered over widely-different parts
of the districts, and many districts and large institutions,
known to be supplied with infected
milk from the dairy X, exempt.
Conclusions.
From the above facts, it will be seen that the outbreak
was somewhat peculiar and did not follow the usual
lines of an ordinary milk outbreak of diphtheria. It is
probable that there was some other factor at work beyond
the infected milk supplied from the infected farm
G, causing the peculiar variation in the localisation of
the disease throughout the different districts, and this
factor appears from the evidence to be certain infected
distributors of milk, who proved, on bacteriological
examination, to be "carriers" of diphtheria. In any case,
there can be little or no doubt as to the effect of distributor
No. 19, who was an actual "carrier," having assisted in
causing the increased local incidence in Croydon, in the
area bounded by Central and Beulah Hills and Church and
Hermitage Roads—an area containing 28 of the total cases
(42) notified in that district, i.e., 66.6 per cent. There is
evidence also that "carriers" Nos. 2 and 12 and "odd"
man E.F. may have exercised a somewhat similar influence,
though to a less marked extent, in other districts.
Though the factor of the infected farm G is proved, the
result of the infection during the outbreak is undoubtedly
peculiar and anomalous in another way, viz., in the
slightness of the virulence of the poison when distributed
through the milk, causing the disease to spread in an
exceedingly mild form as well as irregularly throughout