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effective method of distributing HCN, since they can be "sailed" into
'tween decks or wings of holds, and they are also useful for the accurate
dosage of small compartments. Moreover, the spent units can easily be
collected and removed after the fumigation.
In the hands of a competent Staff of fumigators all the methods
mentioned are effective, and can be applied to small cargo vessels or
large passenger liners without undue risk. But, if the fumigators are
inexperienced or careless or there is imperfect organisation or lack of
discipline, any method of Cyanide fumigation may not only be ineffective,
but is very likely to result in fatal accidents.
In London ships are fumigated only when the holds are empty, or very
nearly so, except when there is definite evidence or strong suspicion of the
existence of rodent Plague on board. In the latter event a preliminary
fumigation with HCN would be undertaken immediately, whether the holds
were full or partly discharged, with the object of destroying as many rats
and fleas as possible and thus diminishing the risk of the spread of the
infection to the shore rats. But, since complete deratisation of a loaded
ship cannot be guaranteed, the vessel would be again fumigated throughout
when empty.
During the year the Ministry of Health, assisted by the Imperial College
of Science and the Port Sanitary Authority, carried out a careful investigation
in the Port of London into ''The Efficacy of the Open Method of
Burning Sulphur for the Fumigation of Unloaded Ships." A full report
was submitted to the October Meeting of the Permanent Committee of the
Office International d'Hygiene Publique in Paris. The general conclusions
were as follows:—
"The experiments—the conditions of which were severe—show
that in the fumigation of an empty ship by burning good quality Sulphur
in trays (in the proportion of 3 lbs. of Sulphur per 1,000 cubic feet of
space) a lethal concentration of Sulphur Dioxide is reached and maintained
for more than the corresponding lethal period. Places where it
is obvious that gas will hardly penetrate must be thoroughly opened up.
If an empty ship is properly prepared for fumigation by the opening
up of closed spaces, either Sulphur Dioxide or Hydrogen Cyanide will
prove an efficient fumigant, but if the ship is not properly prepared,
neither gas will be completely effective."
"It seems clear to us that whilst individual Authorities should be
left a full discretion as to the particular method they prefer to adopt,
all Authorities can safely accept the open method of burning Sulphur
as a practical and efficient means for the fumigation of empty ships in
order adequately to meet the requirements of Article 28 of the
International Sanitary Convention."
(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 fumigation, are
required to have traps set in all spaces where signs of rats are discovered.
The trapping may be carried out by professional rat-catchers or, in some
cases, by members of the crew, under the supervision of the officers of the
Port Sanitary Authority.
(b) Premises in the vicinity of Docks and Quays. The Port of London Authority
constantly carry out methods of rat destruction ashore in the Port. Trapping is the
method principally employed, but the Authority are always ready to test any new method
of rat-destruction that is brought to their notice. The condition of all shore premises is
under the constant supervision of the Sanitary Inspectors and Assistant Eat Officers
of the Port Sanitary Authority, who draw the attention of the officers of the Port of
London Authority to any signs of rat-infestation they may discover.
(4) Measures taken for the detection of rat prevalence in ships and on shore:—
Examination by Inspectors and Assistant Eat Officers, as already described.