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to the spread of malaria. When first taken over by the British about thirty
years ago, the Duars was mainly unbroken, forest; it owes its recent importance
entirely to the tea industry, in connection with which there are in the district some
250 Europeans, a somewhat greater number of babus, and an immigrant popula-
tion of about 150,000 coolies. The labour throughout the Duars is obtained under
the " voluntary system," a system entailing, as we have seen, a more unsettled
population and a more constant influx of immigrants into the district than the
contract system; and the constant movements of the population and the contin-
ual influx of new-comers has led in the Duars to such widespread prevalence of
malaria as probably does not exist over a like area anywhere else in India.

     The most obvious features in the Duars is then the prevalence and intensity
of malaria infection. We shall, therefore, pass briefly in review conditions in res-
pect to this disease, and later see if there are any other conditions likely to be the
cause of Black-water Fever.

     An idea of the universal prevalence of malarial infection may be gathered
from the following list of garden lines showing the endemic index :—

227 H. D,