Medical Officers of the Army of India.
57
ground, and when the water is many feet from the surface, and that this
mode of infection is a much commoner one than that by drinking water,
although the latter doubtless also occurs. As the plasmodium malariœ
is endowed with amœboid movement, the very thin walls of the alveoli of the
lungs and of the pulmonary capillaries will offer but little resistance to its
entry into the blood. I would also suggest that the organisms might also just
as easily make their escape in the same way, and to my mind this is a much
more satisfactory theory to explain how the organisms of malaria leave the body
in order to resume their external life, than the supposition of Dr. Manson that
the interference of the mosquito, or other sucking insect, is necessary to assist
its escape, if, indeed, there is any necessity for such an escape at all, seeing
the unlimited number of these parasites there must be in the soil of malarious
districts. I may add that I have got complete confirmation of the relationship
between the rise and fall of the ground-water and the occurrence of fresh cases
of malaria, in the Nowgong district of Assam, but here there appears to be some
evidence that, during a long break in the rains, there may be a rise of the fever
rate in connection with the drying up of the soil, as, indeed, might be expected
from the fact that the ground-water is much nearer the surface in some parts of
that district than it is in Doranda. In fact it is intermediate between places where
the ground-water is very low and where it is very high and the seasonal fever
incidence is intermediate between what it is in the case of the two extremes.
The exact incidence of the malarial fevers in the rainy season, with
recurrences extending into the cold weather months in proportion to the
amount of fever in the rains, as shown in the accompanying charts, only hap-
pens in places where the ground-water level is low in the dry seasons and rises
rapidly during the rains, and it is worthy of note that chronic malaria is very
rare in such districts, because new infections only taking place to any extent
in the rains, there are eight months in which the poison may be eliminated from
the system before more is likely to be absorbed. On the other hand in
places like lower Bengal and Sylhet, where the water is always much nearer the
surface (in the latter place it was only five feet from the surface at the end of
the dry weather this year), the main incidence of the fever is during the drying
up after the rains, and chronic malaria is of frequent occurrence. The former
fact is accounted for on the supposition that, when the saturated ground is
drying under the influence of the autumn sun, much of the water is evaporated
into the air, and this carries up with it the infecting organisms which are
living in large numbers close to the surface of the ground in the warm moist
soil, and they are then breathed in as before described. The water, and conse-
quently the organisms also, being near the surface all the year round, new
infections can constantly take place and hence chronic malaria is common in
such parts. The further fact that in such places as Dacca and Sylhet the
amount of fever is less when a great part of the ground is submerged, also points