6
Before going further it is necessary for us to indicate the various
influences at work in such a combination and the way in which they
act in relation to malaria.
Labour, whether in India, Africa, or elsewhere in the tropics, is
usually of the kind known as " coolie labour." Coolies are brought
together from far and wide and settled down in labour camps some-
where in the immediate neighbourhood of the scene of the operations.
These more or less temporary camps may contain hundreds or even
thousands of inhabitants. But they resemble neither village nor
town; for the hastily erected huts which form the vast majority of the
dwellings are almost invariably the rudest of temporary shelters, while
the density of the populations on the camp site becomes as great or
even greater than is met with in towns. Such aggregations also lack
the sanitary arrangements, the permanent houses, and the material
comforts of abundant food supply and a sufficiency of comparatively
good water usually enjoyed by urban communities. Such camps,
moreover, are just the size and offer just the amount of aggregation
favourable for anopheles, which can breed over a wide area around and
about them. Their coolie inhabitants are drawn from various locali-
ties, often from different provinces or perhaps even from distant coun-
tries; some come from malarious places, others from regions compara-
tively healthy; some are already infected with malaria, others when
they first arrive are free from infection and very susceptible. Thus
from the very commencement of operations month by month, even
year by year, if the work extends over a long period there is an as-
sociation of infected and susceptible persons eminently suitable for
the great exaltation of malarial infection. Again the more unhealthy
a centre becomes the greater is the loss by death, desertion and migra-
tion, and this necessitates the introduction of new recruits in increas-
ing numbers and at more frequent intervals adding still more to the
extension of the mischief.
Nor is it the immigration factor alone which becomes of increasing
importance; for by the very nature of things large numbers of the des-
titute and needy and those feeling the pinch of necessity are in the first
place gathered together along with the miscellaneous crowd of workers
and not only so, but the very conditions associated with aggregation