14
cycle of the parasite. We have never heard of any investigation
having been undertaken with the object of ascertaining in what way
malaria has been influenced, and whether or not there has been any
increase in anopheles mosquitoes in the specially unhealthy tracts or
during the unhealthy years.
There is, it is true, a way, but an indirect one, in which changes:
in the great rivers may seriously influence malarial incidence and this
has already been well described by Chatterjee, who points out that
by the shifting of the river channels to the east, towns and districts
once prosperous and flourishing suffer from loss of trade, industries
decay, and populations become subject to economic conditions favour-
able to malaria. But though this has no doubt played its part,
it appears insufficient to explain why epidemics have specially
prevailed during particular years in. certain parts of the country.
Commission after Commission reporting upon the question have
invariably dismissed the suggestion that the making of roads and rail-
ways was concerned in causing obstruction to the drainage.
A glance at the map of Bengal will show that the districts that
have been from time to time involved in epidemic malarial outbreaks
bear a certain relationship to Calcutta; that they are practically
identical with the great industrial areas to the north and west of the
city and the expanding fan of railways that link the metropolis to
the great districts on the north-east and north-west. Above all
the recurring epidemics have often picked out in a curious
manner, parts like the great coal districts of Burdwan, the mill dis-
tricts of Hooghly, and other centres of industrial activity.
Before hazarding an opinion as to how far this is mere coincidence
or real association, let us consider the local history of this part of
Bengal. Prior to 1860 there is little evidence of the existence of any-
thing like the movement towards the immense industrial expansion
of recent times; but from about this time there commences a period
of phenomenal activity in commercial enterprise and an era which saw
the inauguration and completion of enormous public works. With
in a decade three great canal systems, the great railways, a vast net-