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INDIA

a subject of paramount interest to all students of Indian
physiography. The locality of its original development is
limited by the physical conditions of altitude and latitude.
Above a certain elevation (which may be roughly defined
as about 7000 feet above sea) it apparently does not
germinate, and it is not to be found in north latitudes, the
limits of which are as yet undefined, but which are at any
rate north of India. It is probably not far from the
truth to say that every European who passes any continued
 period of his life in the plains or in the climate of
the lower hills which border the higher ranges is more
or less impregnated with malarial poison. Equability of
temperature is the great safeguard against its development,
and therefore districts contiguous to the sea are more
exempt from fever than those farther inland. At the
same time nothing seems to arouse the dormant energies
of the malarial microbe more than sea air after a long
inland residence and apparent freedom from its effects.
A change from the moist, warm climates of Southern
India on the coast to the dry and apparently invigorating
atmosphere of such hills as those of Baluchistan will
frequently accelerate the disease and decimate a regiment
 before it has had time to acclimatise. The
origin of all malarial germs seems to lie beyond dispute
 in decaying matter subjecled to the influence of
heat, and the distributing agent seems as certainly to be
a particular species of mosquito ; but it has hardly yet
been fully ascertained how far locality influences the varied
action of the fever germ. or tends to the reproduction of
the mosquito.
Throughout Northern India the unhealthy season is
reckoned to follow immediately after the rains. It is
then that the earth is saturated with moisture, whilst the
sun’s rays are yet strong upon it, and there is the first
touch of the coolness of coming winter abroad in the air.
The jungles of the Tarai at the foot of the Himalayas, as
well as some of the low valleys amongst the mountains
themselves, become rank with malaria. No European
enters them, and only such natives as appear to have