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degree of controlling malaria in the great districts and provinces of
India.
Not only have all successful anti-larval campaigns been asso-
ciated with the free use of quinine, but they have in every case dealt
with comparatively insignificant populations, in some cases with
communities no larger than those to be found upon a single tea
garden; and they have involved comparatively enormous expense
reaching in some cases several pounds sterling per head of the popu-
lation.
It is impossible to argue from such examples the probable effects
of large drainage operations or measures directed against the mos-
quito alone, and we have already shown how small a relation mere
numbers of anopheles often bears to the prevalence and intensity of
malaria when conditions unfavourable to the human host are present
in a marked degree. This being so, it is impossible with our present
knowledge to be certain that the inauguration of vast drainage
schemes at a cost of crores of rupees will have the slightest appreciable
effect in reducing malaria in Bengal ; and it is quite possible, on the
other hands, that without the most careful control of the conditions
relating to the employment of labour on such undertakings grave dan-
ger may be incurred, and this very measure far from reducing malaria
may, for a time at least, serve actually to increase and intensify it;
while the larger the scheme, the greater would be the risk arising from
uncontrolled aggregation of the labour necessary for the performance
of the work.
As to the repeated statement that drainage of a country
must necessarily produce a mitigation of malaria by reducing the
numbers of anopheles mosquitoes, we may surmise, bearing in mind
Celli's definitely-expressed opinion regarding the Roman Campagna as
well as our own experience in India, that the improvement that
follows such operations may often be largely secondary in nature
and bound up to a great extent with the permanent settling of
populations and other conditions favourably affecting the human
host.
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