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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 was 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 kerosine, which is sufficient to destroy the fleas on the subsequent batches
of rats placed in the bags.
Before these arrangements were put into operation, on 1st August, details were
discussed with the Docks and Warehouse Manager of the Port of London Authority,
the Secretary of the Seamen's Hospital and Professor Hewlett, who cordially
co-operated in the scheme, which is now working smoothly and efficiently, thanks to
their assistance.
(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 anv other communication with the shore, unless the same be
i/
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. Poll 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.