58 Scientific Memoirs by Medical Officers of the Army of India.
to the conclusion that malarial infection is mainly through the air, for at such
times the organisms would : less readily find their way into the air by either
displacement from the ground or by evaporation from a saturated soil. In
short, I am inclined to think that all the main facts with regard to the seasonal
incidence of malarial fevers are explainable in great part by the height and
variations of the ground-water level, but as these vary in the most extraordinary
way in even very similarly situated places, all the local circumstances have to be
taken into account before the explanation which I have here advanced is reject-
ed in any given case. A good instance of such a variation, which has also a
practical bearing, happened in the case of the Doranda lines with which I will
conclude this paper.
On the same day that the water level in the regimental lines was only
5¼ feet from the surface of the ground, it was 25 feet down only 300 yards
away on the parade ground, although there was not a difference of more than
three feet in the level of the two places. The high level in the lines was due
to a road having been made with only one small culvert in it, (and that on too
high a level) which obstructed the surface drainage of the lines. This is to be
remedied on my suggestion as far as possible, but unfortunately it could not
be done before the rains of this year set in, so I am unable at present to give
the result of this measure. It shews, however, what apparently slight things
may modify very materially the health of a site, for I have no doubt whatever
that if the lines had been where the parade ground is, there would not have been
half the amount of fever that there now is in the wet season. In 1894, for instance,
the water reached the level of the mouth of one of the wells, a rise of from 35
to 40 feet from the lowest level at the end of the hot weather. Until measure-
ments of the ground-water were taken there was no suspicion that the surface
drainage was so deficient. The lesson is obvious, and I would suggest that
such measurements should be taken, for a year if possible, before a site for a
station or cantonment is chosen in any malarious country, as this simple measure
might prevent the necessity of abandoning posts after the expenditure of
considerable sums of money on buildings, etc., on account of the amount of
fever in the place, as has happened before now. If, for instance, two or more
sites appeared to be about equally favourable, and time permitted, a well should
be sunk in each and measurements taken, which would show in which site the
ground-water is lowest and least variable. This site would be the least malarial.
I have recently met with other instances in certain tea garden coolies' lines
where by means of taking the ground-water levels, I have been able to show
that the nearer the water is to the surface and the more it varies the greater
is the fever rate, so that the Doranda case is not an isolated one. Many
more observations in places whose ground-water levels differ widely will be
necessary before a general law of their influence on the prevalence of malarial
fevers can be formulated, but it is hoped that this contribution may lead to
renewed attention being given to the subject.