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ently high to justify (on that ground alone) any feeling of
alarm with regard to the health of the population.
My analysis tends to show also how irregularly small populations
vary; how uncertain therefore, in the intervals between
successive censuses, must be our estimate of their numbers;
how questionable must be the accuracy of the death-rates which
we deduce from them; and how little significance differences in
the death-rate of .2 or .3 per cent. must for the most part have.
But supposing a death-rate to have been ascertained with
perfect accuracy; what does it teach? what do we learn from
it ? The prime fact of course is that out of so many persons
living, so many persons have died in a given time. Experience
has shewn that in ordinary years death-rates vary within comparatively
narrow limits; that in the presence of severe outbreaks
of epidemic diseases death-rates become augmented, and often
very seriously augmented; that in certain localities which are
generally assumed to be of inferior healthiness (such as large
towns) the death-rates are mostly higher than they are in certain
other localities (such as country districts) which enjoy the
reputation of comparative salubrity. And on these and other
grounds it has been assumed that the death-rate is a measure
of the health of a population, and that the fluctuations of the
death-rate imply corresponding fluctuations of health. To a
certain extent this is true; but it is true only of the margin
which remains after necessary deaths, (if I may use the expression)
have been eliminated (and these constitute the great bulk
of a mortality); and after the effects of all influences tending to
disturb the due proportion between the young, the middle-aged
and the old, the healthy, the sick and the dying have been investigated
and allowed for. On the effects of those deaths
which I have termed necessary upon death-rates I need not now
enlarge. I may simply mention that I suppose such deaths to
include amongst others all deaths from old age, from inherited