12
It might be supposed at first sight that plague which broke out at the
end of 1896 was solely responsible for the sudden alteration in the character
of the seasonal mortality, but it cannot be entirely ascribed to this cause, as
a similar alteration in the character of the seasonal mortality took place in
1864—1866 and again in 1876. In 1863 51 per cent. of deaths were recorded
in the period June to December, but two years later, co-incident with au
increased mortality totalling nearly 10,000, the deaths occurring in the dry
season nearly doubled in number and only 37 per cent. of the total took place
in the period June to November. In 1894 only 50 per cent. of the total
deaths took place in the dry season, but during 1895 and the following years a
rapid increase took place in the deaths recorded at that time of the year, and in
1903 over 70 per cent. of the total deaths took place in that period. Since
then there has been a gradual return to normal again and in 1910 over
45
32. An examination of the return of male and female deaths for a
number of past years supports the view that, co-incident with the advent of
plague in Bombay increased migration has taken place, leading to an excess
of males in the population and causing a complete alteration in the ratio of male
to female deaths recorded in the City.
Sex Mortality.—The following table shows the ratio of female to male deaths
recorded in the City from 1886 to 1909 :—
Year
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
Female deaths
to 1,000 male
deaths.
931
910
872
892
893
925
951
866
903
855
826
747
Year.
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
Female deaths
to l,C00 male
deaths.
692
693
746
675
737
745
717
763
787
761
768
756
It will be noticed that the decrease in the proportion of female to male
deaths, which took place in 1896, became greater in subsequent years, the
maximum variation being in 1901, the year of the Census. Prom 1901 until
1906 the ratio of female deaths to male gradually increased again, but since
that year there has been a slight decline. As a general rule, when dealing with
large populations, there is only a slight difference between the death-rates of
males and females living under the same conditions ; and the only explanation
that can be given of the variations shown in the above table is a frequent
alteration in the proportion of the two sexes in the population.
33. Effect of Migration upon Mortality.—If we were dealing with a
permanent population of known number it would be reasonable to assume that
an increase or decrease in the total number of deaths occurring from year to
year was due either to a greater or a lessened prevalence of disease; and
that this in turn was directly related to the climatic, economic or other con-
ditions obtaining at different times. Eut the factors which determine the
variations in the total mortality of large cities in India are usually of a
complex nature. In Bombay migration of the population is a factor of
tremendous importance both as regards the real and the apparent health
conditions of the City. As has already been mentioned, the population of
Bombay is augmented each dry season by many thousands of persons most of
whom leave the City again before the onset of the south-west monsoon. There
are strong grounds for believing that this periodical movement affects at least