4
in six or seven months. The epidemic of cholera that left Bengal in the
spring of 1818 reached Ceylon in January 1819; but, with all the facilities
for rapid communication introduced during the last half century, we find
that the great body of moving cholera in the last epidemic invasion, which
fell upon the Central Provinces in the spring of 1868, did not reach Ceylon
until May 1870. A proper appreciation of this fact will, I think, indicate that
in the movement of cholera from its endemic home, there are other agents than
human intercourse at work. An attempt will be made by and bye to estimate,
in their order of relative importance, the various factors concerned in the
progressive movements of epidemic cholera. It will be only necessary in this
place to recognize the fact that cholera does move in accordance with its own
laws, and that a new epidemic movement in the Bengal Provinces is (so far as
the facts of the past admit of an opinion being formed) sure to be felt, at a date
more or less remote, not only in the tract of country to the north-west of Bengal,
but also to the extreme south-east of Asia, including Burmah, the Straits Settle-
ments, and China, and to the extreme south of the Madras Presidency, not
excepting the Island of Ceylon.
Cholera does not
move into the Madras
territory by the short-
est route.
7. There is one other point to be noticed here in regard to the movement of
cholera out of the endemic provinces, and it is, that an
epidemic does not usually take the shortest route, but, as it
so happens, the route of greatest population and traffic. A
map of India shows that the actual distance between Calcutta (the centre
of the endemic field) and Madras is the shortest along the Coromandel
Coast ; but there is only one instance recorded in which cholera has advanced
epidemically along the coast line down to Vizagapatarn, and that was in the year
1818, where, according to Scott's narrative, it travelled in this direction as well as
through the Central Provinces and Hyderabad. The evidence adduced by Scott
does not make it quite clear to me that cholera actually took this coast route,
but it is possible that movement did occur in this direction, as well as by the more
common route through the Central Provinces. In the two invasions of 1859
and 1864 it is abundantly clear that cholera did not advance along the Coro-
mandel Coast line from north to south, but that the districts on the coast, from
Vizagapatam downwards, were invaded subsequent to the overflow of the cholera
wave in Nagpore and the Deccan.
The ordinary course of the cholera that finds its way into the Southern
Presidency is at first north-west through Chota Nagpore and Allahabad, then
west and south through the Central Provinces to Bombay and the Deccan.
The readiest way for cholera to reach the Vizagapatam, Godavery, and Kistna
Districts, when an epidemic wave starts out of the endemic field, would be through
the districts which lie immediately to the north of Cuttack and Granjana, but it
chooses, by preference, the long and circuitous route just indicated. What the
actual explanation of this movement may be is not now the question. It is
sufficient for the present that I draw attention to the fact.
Influence of moun-
tain barriers in direct-
ing the movement of
cholera.
8. In studying the movements of cholera I think one cannot help being struck
by the circumstance that a mountain barrier frequently
appears to offer an insurmountable resistance to the progress
of an epidemic.
The great Himalayan Range, running in a north-westerly direction across the
Asian continent, appears to be practically effective in limiting the march of