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drains of the infected house were not found, on testing, to
be defective.
No cases of plague, nor of suspected plague, nor of Asiatic
cholera, nor of suspected Asiatic cholera, have been notified
during 1910, within the Borough.
In the case of each of the 1368 infected houses, an inspection
was made, and the drains and sanitary fittings were
tested with chemical, with the following results as tabulated:—
(a) 101 (i.e., 7.4 per cent.) were found to have defective
drains, i.e., gave results with the tests;
(b) 547 (i.e., 40.0 per cent.) were found to have
defective traps, fittings, or appliances;
(c) 720 (i.e., 52.6 per cent.) showed no defects.
It will be noted that only 7.4 per cent. of the total infected
houses showed, with the test, defective drains, no results
being obtained from the tests in the other cases; and 40.0
per cent. showed defective traps, fittings and appliances.
Drains and sanitary fittings are tested, as a routine, in all
infected houses, though it does not follow that, when defects
are found, such defects are the direct causes of the diseases
under investigation. They may indirectly be so.
The test used as a routine is the chemical or smoke test,
and when a result is obtained, the drain (tested) is tabulated
as defective, but, when no result is obtained, it would
be wrong to state that, therefore, the drain (tested) was
sound. A negative result proves nothing with the chemical
(or smoke) test. The hydraulic (water) and pneumatic (air)
tests are the only reliable tests, but too severe for the routine
testing of drains of old buildings. The pneumatic (air) test
is comparatively new, and most delicate, but it is not much
used in London at the present day. All new drains when
laid are tested with water (hydraulic test), both in sections
and as a whole.
Bearing this explanation in mind, the above statistics are
still useful as showing that, year by year, the number of