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A remarkable and predominant feature of this outbreak
was its restriction to this very circumscribed area.
Investigations made as to origin of the outbreak,:—
(l.) Milk Supply.—Of the first 7 cases notified between
August 27th and September 7th it was at once noticed that
4 of them obtained their milk supply from the same source.
Investigations were therefore at once begun to see if any evidence
could be obtained to justify action being taken to prevent
the sale of milk from this source. Very careful and exhaustive
enquiries were made concerning this milk supply and the
milk traced back to its original sources, but no evidence could
be obtained that the milk was in any way contaminated either
at the farms from which it originated, or in transit, or in
process of distribution. During the course of the outbreak
this negative evidence was confirmed by the fact that cases
were occurring in the special circumscribed area in houses
which had not had any milk at all, and also in houses supplied
from entirely different sources; while on the other hand no
cases were occurring in other parts of the district in which
the same milk was being distributed.
It appeared evident that the milk supply was not the
cause of the outbreak, and therefore no action was taken to
stop supply of this milk.
(2.) Water Supply.—Attention was next directed to the
water supply, which is supplied by the Metropolitan Water
Company by a branch from the main which comes down the
Green-lanes.
Samples of water were taken from taps direct off the
main in houses of two of the streets in New Southgate most
affected, and analysed both chemically and bacteriologically
for evidence of sewage pollution.
The reports in both cases were as follows:— "A very
good sample of drinking water. No indication whatever of
any sewage pollution."
(3.) Sewerage.—The sewer, house drains, etc., were
inspected and no defects found.
The sewerage in this part of the district is on the same
dual system of foul sewers and surface-water sewers as
obtains throughout the whole district. The sewers and house
drains in this neighbourhood are for the most part of recent
construction and in good condition. During the summer
months they are flushed regularly once a fortnight.
(4.) Shell Fish, Fried Fish, and Ice Creams.—The
question of shell fish, fried fish, and ice creams as a possible
source of infection was also carefully investigated, but little