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24
excess of the bacterial standard of 100 microbes per cubic
centimetre; on one occasion the number of microbes in the
sample after filtration being as many as 2,368, and in another
1,396 per c. c.
Of the 8 filters, numbers 2, 3 and 5 were found inefficient
each time that a sample was taken, and not one of them was
efficient on each occasion. Of 25 samples of water taken
after filtration there was an infraction of the standard in as
many as 13.
Fortunately on no occasion was any pathogenic organism
found even in the samples of Thames water taken. It must
not, however, be forgotten that by the present method it is
difficult to detect typhoid bacilli even in a sample to which a
small quantity of typhoid material has purposely been added.
Inefficient storage and filtration is, therefore, a constant
source of danger, which might lead to an epidemic should
the necessary combination of circumstances occur.
During the past twelve months experiments have been
made which prove that typhoid bacilli and the bacillus
enteriditis sporogenes, which is considered to be the organism
that causes epidemic summer diarrhoea, can flourish in
polluted soil. Additional weight is thus given to the opinions
mentioned in my report for the year 1895, namely, that leaky
mains and service pipes might be one of the causcs of typhoid
fever and summer diarrhoea.
I then called your attention to the fact that in many
places the depth of the mains below the surface was less