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result; yet in reality this is quite an inadequate conception of the true state of
affairs. We have been fortunate enough to see in several parts of the Tropics
operations involving " Opening up of the soil." Such operations always involve
certain conditions. The most important is the formation of enormous camps of
coolie labourers and their families, drawn from far and wide throughout the
district, or even from distant countries. In such camps of far more importance
than mere extra facilities for breeding of anopheles are certain conditions: the
mixture of races and classes involving admixture of susceptibles with the infect-
ed; the depressing effects of hardship, especially affecting the weaker, who in turn
by becoming malarial disseminators take their part in the vicious cycle; crowding
of the population into communities larger than occur in ordinary rural conditions
and not large enough to derive the benefits to be got from the urban; and many
other factors we need not specify. Suffice it is to say that camp conditions play
into the hand of malaria more than any others known to us; so that in these
huge labour camps we find malaria in its intensest and most pernicious form.

   Naturally the Europeans and others employed in supervision suffer in the
general trouble, since in their ignorance they dwell not apart from but in the midst
of the natives. The belief that malaria comes from the opening up of the soil
is therefore based upon fact; but it is not the miasmatic exhalations or even the
extra facilities for the breeding of anopheles, though this too helps in the general
vicious cycle, that is responsible. Its origin is bound up in the general conditions
inseparable from the existence of great labour camps in the Tropics. To em-
phasize the condition, which is a very real one, we may call it the factor " of
Tropical Industrial Aggregation. "

   Much of the area we are discussing has only been opened up and occupied
within the last fifty years and vast tracts are still jungle or virgin forest. It
owes its recent importance mainly to the tea industry, of which it is the chief
site; and our interest in the district centres in the conditions on the tea gardens,
of which alone we have the knowledge necessary to enable us to speak.

   When we come to discuss the incidence of malaria among tea-
garden popula-tions, we find that there are several points relating to the character of such popu-
lations which require consideration. The introduction and gradual development
of the tea industry has resulted in the necessity of employing large working popu-
lations; and the difficulties, encountered in obtaining a supply of labour from among
the indigenous local population has led to the introduction of vast numbers of
immigrants from various parts of India.

   Fortunately for Assam immigration in this province has gone on under
a system known as " indentured labour " which regulates to some slight degree