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The following facts, however, go a long way towards
doing this :—
(l.) Milk from the same source as that supplied to
these 21 infected houses was supplied also to a large
district outside the infected area. In fact, the number
of houses in the infected area supplied with this milk
formed only a small proportion of the total number of
houses supplied with milk from the same source. Outside
the infected area only 3 cases of typhoid fever
occurred in such houses, and taking the total number of
houses supplied with milk from this same source, the
number of houses infected becomes reduced to 9 per
cent.
If this milk supply had been the cause of the outbreak
it would have been very improbable that the latter
would have been confined to so limited and circumscribed
an area, but would have been spread over the whole area
supplied with this milk.
(2.) These houses were not the first houses attacked,
but were distributed evenly throughout the whole of the
44 houses infected during the outbreak. So that it cannot
be argued that the outbreak originated in these houses
supplied with milk from the same source, and from there
spread to the remainder by direct or indirect infection.
(3.) The inhabitants of these houses in which the
outbreak occurred all belong to the poorer working
classes, who only use milk in small quantities in their
tea, and occasionally for puddings, and seldom, if ever,
drink milk by itself.
If milk were the cause of the outbreak it would have
been expected that the somewhat better classes, who
drink more milk, would have been attacked more than
the poorer classes. But this was not the case.
(4.) The evidence of the age constitution is also
against milk being the source of the disease. Taking
primary attacks only, of which there were 41, 22 occurred
in those of 15 years and under, and 19 in those of over
15 years. If milk had been the cause of the outbreak
one would have expected a larger incidence of the disease
in those under 15 years.
(II.) Water Supply.—There was no evidence obtained
to throw suspicion on the water supply. Moreover, if the
water supply had been infected it is certain that the outbreak
would not have been confined to the limited and very circumscribed
area as it was, but would have been spread over the
whole of the area supplied by this water.