29
that time it steadily declined until the end of April. For these five months the
total number of deaths from all causes was 81,618 including 23,256 deaths over the
normal number, which, in the absence of any other cause, may be taken as the plague
mortality.
In the second epidemic the mortality did not reach, epidemic proportions until
the beginning of January 1898, and it attained its maximum of 165·00 per thousand
in the third week in March on a population of 715,400, having taken a fortnight
longer to reach it than in the first, and declining, as did its predecessor, at the end of
April. The total number of deaths from all causes for the four months of this epidemic
was 29,509, and of which 18,651 are over the normal and may be accounted plague
deaths.
The third epidemic started at the end of the first week in January, just a week
after its predecessor. It has followed the curve of the second visitation almost
exactly, attaining its maximum death-rate of 161·5 per thousand in the same week
on a population of 774,500 souls. The length of this epidemic was five months, for
it did not decline, as did che previous ones, at the end of April, but a month later,
and the total number of deaths from all causes was 34,241, being 22,859 over the
normal.
The Chart distinctly shows that the third epidemic, though not so virulent as
the first, and not attaining such a high death-rate by 3·5 per mille as the second, was
considerably worse than the second in its length, and in its total number of deaths.
It also shows that the generally accepted idea that plague leaves us with the
advent of the hot weather, is not borne out in the third epidemic, which ran prac-
tically until the end of May, and the fact that a large proportion of the population
sleep out of doors in the hot weather is not such an important factor as is supposed.
Another point in the Chart worth noticing is that all three epidemics have as
nearly as possible commenced three months after the end of the monsoon. In 1896,
the epidemic started in the first week in December, the rains of that year having
ended in the first week in September ; in 1897 and 1898, the completion of the
monsoon occurred about the first week in October, and the second and third epidemics
started as nearly as possible at the end of December and the first week in
January.
General Observations.
In reviewing the two Charts now completed for the three epidemics, it is
interesting to note some of the points which stand prominently out in them, and which,
if not altogether definite, are yet valuable.
It may be noted from Chart No. 1, that a low temperature in all three epidemics
has had the effect of increasing the disease, and that dry Northerly and Easterly
winds clearly have an unfavourable influence, often immediately, on the mortality.
The coincidence mentioned under the notes on Chart No. 2, that plague becomes
epidemic three months after the completion of the monsoon, tend rather to point that
a period of time elapses either of immunity for the population or of dormancy for the
plague bacilli.
Each year the disease appears to become epidemic at a later period than its
predecessor, and it will be interesting to note, should there be a fourth epidemic,
whether there is anything in the coincidence of the mortality becoming epidemic
three months after the monsoon is over.