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18
Sulphur di-oxide is probably the safest and best gas for the destruction
rats on board ship, and several methods of using it have been tried :—
First. Sulphur has been burned in the holds of ships. It is difficult
to ensure a more than 5.5 percentage of gas by this means, and there is
the additional risk from fire.
Second. Compressed and liquefied gas has been used, but owing to
the low diffusion power and density of the gas in this state it has not
been found very successful. In one instance, although dead rats were
found, yet live rats in cages within six feet of the empty cylinders were
uninjured. I purpose repeating this experiment when a favourable
opportunity occurs, and hope to obtain better results.
Third. By pumping or forcing into vessels gas generated in a special
apparatus carried on a barge or other conveyance and ranged alongside
the vessel.
Twenty-eight vessels have been fumigated with sulphur di-oxide, and a
great number of rats have been destroyed in this manner. On one vessel
over 1,000 rats have been destroyed by this method. It would seem
that this is the most efficient way of dealing with rats, but inasmuch as it
cannot be done while cargo remains in the ship without running great risk of
damaging the cargo, it has, therefore, to be done when the vessel is empty,
and, it is to be feared, many of the rats have got ashore.
During the past year, owing to actual or suspected cases of Plague
occurring on board vessels, it has been necessary to take the names and
addresses of all persons on board, which names and addresses have been sent
to the Medical Officer of Health of the district to which the said persons are
proceeding.
In a small percentage of cases these notifications are returned by the
Medical Officer of Health, with the remarks :—
" Not known at address given."
" Formerly lived here, but not so at present."
" No such street or address known."
As the practice of quarantine has been abolished in this country and the
above precautions substituted, it will be seen that a defect exists.
The Medical Officer, when inspecting persons, asks for their names and
addresses, and unless he has any reason to doubt their good faith they are
allowed to land, with the result that it is often impossible to trace some
persons, and if the practice is found to continue and increase it will become
necessary to adopt stronger measures, e.g., the detention of all persons on
board whilst enquiries are made as to whether the addresses given are genuine,
and the persons known or expected to arrive home.