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78
DISINFECTANTS.
The disinfectants and other chemicals in use in the Public Health Department and in
other branches of the Corporation's service, have, as in the past, been supplied under a contract
prepared by your Medical Officer of Health.
They are used for deodorising and denaturising unsound meat, disinfecting public
conveniences, streets and roadways, premises after infectious diseases, etc.
Special attention was given to the thoroughfares in the vicinity of the Billingsgate and
Smithfield Markets, the former of which presents certain difficulties in the matter of deodorisation
in the summer months.
Very few complaints were, however, received of offensive odours necessarily associated
with the fish trade.
RAT REPRESSION.
The tables set out on page 79 indicate investigations and advisory work which has been
undertaken under the Rats and Mice (Destruction) Act, 1919. From this summary, it
will be seen that 983 buildings occupied by 2,134 firms were inspected, and that 348 were
found to be rat infested. One or other of the rat catchers working in the City was engaged
by 155 business firms. Poisons were laid down in 397 cases, varnish traps were used in 212
cases, breakback, wire and other traps in 368 premises, Cats or dogs were kept by 151 firms.
Complaints or applications for advice have been received in 140 instances. The work done
in addition to the use of poisons, traps, and animals, included rat proofing in 303 instances,
and the repair of drainage defects in 1,076 instances. Ready compliance with the suggestion
to rat proof has been a feature, and when this is properly carried out, combined with the
elimination of hiding places, it has proved a valuable factor in combating the rat trouble.
It cannot, however, be relied upon absolutely to exclude rodents from buildings. The
receipt of crates and cases from the docks is a frequent source of rat infestation, and ingress
through open doors and windows, especially roof doors provided for exit in case of fire, is
readily obtained.
The Rats and Mice (Destruction) Act, 1919, lays the duty of disinfesting premises upon
the occupiers ; this is one of the difficulties experienced in regard to rat proofing, which
so often involves structural alterations, and is logically the work of the owner.
It is not possible to report even approximately the total number of rats killed. Messrs.
William Dalton & Sons, one of the firms principally engaged in this work in the City, inform
me that they killed 19,215 rats in the City during 1930.
The substitution of old buildings by modern structures, and the constant attention to
drainage and sewage work, have probably resulted in a decrease in the rat population.
So far as palliative measures are concerned, we have continued to obtain very satisfactory
results from the Varnish Trap.

No poison was used in the sewers during the year.
The number of drainage reconstructions carried out under the supervision of inspectors
of this Department is set out on page 79.