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20
The rats from Tilbury Dock are sent by train from Gravesend to Greenwich,
where they are collected each morning by one of the Staff and taken to the laboratory
on his way to work.
It is not found possible to dip the rats on the Docks in a flea-killing solution,
but it has been arranged that the bags containing the rats should be dipped in kerosine
at the laboratory. The bags returned empty to the rat-searchers are therefore
saturated in lerosine, which is sufficient to destroy the fleas on the subsequent batches
of rats placed in the bags.
(2) Measures taken to prevent the passage of rats between ships and shore
The Port of London Authority have made Bye-laws requiring the Master of
every ship to cause all ropes and mooring tackle used for securing ships, either to
the shore or mooring buoys, to be fitted with guards, approved by the Authority, to
prevent rats passing from the ship to the shore, and to cause all empty cases, packages
and barrels to be examined before landing, to ensure that no rats are contained
therein. The removal of rats (alive or dead) from ships without previous consent in
writing of the Superintendent, is prohibited. Bye-laws also prescribe that, when the
discharge or loading of cargo or the landing or embarking of passengers is not actually
proceeding, one gangway, whitened for a length of 10 feet at the end next the vessel,
may be used as a communication between the ship and the shore, and that the Master
shall not have or allow any other communication with the shore, unless the same be
fitted with guards, approved by the Authority, to prevent the passage of rats.
These Bye-laws are enforced by the officers of the Port of London Authority,
and the Sanitary Inspectors of the Port Sanitary Authority also call upon Masters
to put guards on their mooring ropes. But the well-known difficulties in regard to
the proper application and maintenance of position of rat-guards constantly occur,
and it cannot be said that the mooring ropes of the majority of ships in the Port of
London are at all times so guarded that a rat could not use them as a means of reaching
the shore. There is no doubt that rats very seldom voluntarily run along mooring
ropes, and the view is held that such rats as get ashore do so usually by some easier
means or accidentally in cargo.
(3) Methods of deratisation of:—
(a) Ships. The methods employed for the deratisation of ships are:—
(1) The burning of Sulphur at the rate of 3 lbs. per 1,000 cubic feet of
space, the period of exposure of vessels to the Sulphur Dioxide gas thus
generated being not less than six hours. Roll Sulphur, of good quality,
is used, and is burned in large shallow trays. Owing to the large burning
surface thus obtained, considerably more Sulphur can be completely
burned in one container within the six hours than is possible when
buckets or pots are used.
(2) The generating of Hydrocyanic Acid gas from "Zyklon 'B'" or from
liquified Hydrogen Cyanide, there being several modifications of the
latter process. If any new method of application of Hydrogen Cyanide
is brought forward, the Port Sanitary Authority always test its efficiency
by concealing test animals on board the ship, and, further, require to
be satisfied that the method does not expose the fumigating Staff to
any unavoidable danger. The concentration of Hydrogen Cyanide
required is approximately 0.2 per cent., and the shortest period of
exposure two hours.
The figures given in Tables "H" and "I" are no indication of
the relative efficiency of Sulphur Dioxide and Hydrogen Cyanide as
fumigants, because one large passenger line fumigate their vessels
regularly every voyage with Cyanide for the destruction of insects, and
these vessels are almost, if not absolutely, rat free.
(3) Trapping. All vessels from Plague-infected ports are required to have
traps set on board, in order that specimens may, if possible, be obtained
for bacteriological examination. All other vessels, on which there is
evidence of rats, but not of such a number as to justify a demand for