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It will be seen that at ages 10-15, the female pulmonary cases exceed the male by 51, or 31 per
cent. The contrast between the sexes at this age in mortality is even greater than in the cases, the excess
being 150 per cent. in 1921. Generally speaking the deaths from pulmonary tuberculosis in London
at the age 10-15 among females are about twice the figure for males, while on the other hand the cases
are not more than about 30 per cent. in excess. The difference between the mortality of the sexes at
the age group does not appear to vary in any marked degree with social condition. Reference may
be made on this point to the table in the report for 1911. p. 42.
The question of the influence of migration of population upon rates of mortality and especially
upon phthisis death-rates has been examined from time to time by statisticians. Thus Noel A.
Humphreys (Statistical Journal, March 1897, p. 76) observed that "Dr. Wm. Farr, formerly President
of their Society, very frequently referred to this migration into towns in his reports. He pointed out
that the deleterious effect of residence in towns was masked to some extent by this migration; that
there were undoubtedly a certain number of these healthy country migrants, domestic servants, shop
assistants and the like, who after a few years of town residence, under the influence of failing health,
returned to the country and in some instances died there." In the Journal of the Institute of Actuaries
(vol. XVI., 1872), there is a paper by Thomas A. Welton "On the effect of Migrations in disturbing
Local Rates of Mortality, as exemplified in the Statistics of London and the surrounding country for the
years 1851-1860." This paper, starting from the standpoint of Farr, is devoted to study of the effect
of resort of sick persons to country districts upon the mortality of such districts. Beginning with
researches into the comparative mortalities in different parts of Lancashire and Cheshire, Mr. Welton
was led to compare the figures for the Metropolitan Division with those obtained for Liverpool and its
neighbourhood. The analysis of the 23 Tables appended to his paper is replete with interest and
suggestion. The main outcome may be expressed in the words of Mr. Sprague, one of the speakers in
the discussion on the paper, who said: "It showed how the rate of mortality in country districts at
certain ages was increased, not only by the migration of unhealthy persons from London to them, but
also by the migration of healthy persons from them into London. It was obvious that the migration
of unhealthy persons from London into the country would have the effect of lowering the mortality in
London and increasing it in the country; but it was not quite so obvious at first sight that the migration
of healthy persons out of the country into London would have the same effect of raising the rate of mortality
in the country. But when attention was directed to that point, it became quite clear that the
migration of healthy persons out of the country would leave behind a body of persons whose vitality and
whose health were not up to the average, and therefore the rate of mortality amongst these persons
would be higher than if there had been no migration."
Ideas with regard to the influence of migration have undergone considerable development in
recent years and the subject has been referred to from t) time time in these annual reports. In the
report for 1920 (pp. 14 and 15) the extent to which the London phthisis death-rate at higher ages may
be raised by immigration of phthisical men is studied. The whole question of "internal migration"
has, moreover, been recently considered by Dr. M. Greenwood in his Milroy Lectures, in which he has
examined more particularly the effect of life in towns on young country people. It is hoped that at
no distant date he will also discuss external migration, i.e., the influence upon phthisis death rates exerted
by movement of population between the several countries and continents of the world.
In last year's report (p. 13), two points of special interest with regard to alterations in the phthisis
death rate were commented upon:—(i.) The development of a marked increase in the death rate, subsequent
to 1914, in contrast with the decline exhibited for half a century previous to 1914; this rise
was no doubt in part due to the fact that the outbreak of the war practically stopped emigration from
the country. (ii.) Dr. Tatham some fifteen years ago commented upon the shifting of maximum age
incidence of phthisis from young adults to middle life; the phenomenon noted by him may be due to
the increasing outward movement of phthisical persons, especially at the young adult ages, from the
middle of the last century onwards; since 1914, a backward movement had, it was pointed out, set
in, the maximum rate of mortality reverting again towards the younger ages (p. LXX Ann. Rep. Reg.
Genl. for 1918).
The question of special interest which now arises is that since the resumption of intercommunication
and traffic between the civilian population of this country and the outer world, there has been manifested
a tendency for the statistics to show a reversion (in respect of both the phenomena just referred to) to
the pre-war conditions. Study of the actual deaths in men and women at the different ages in the
years 1911-21, shows this, and the facts afford strong support for the view that the influence of migration
is a very important one. Thus considering first the war period, 1914-18, the increase in the number
of deaths among females aged 20-40 in these years was marked, and the deaths among males aged 20-40
remaining in the country showed but little decrease despite the great reduction in the numbers of such
males owing to military exigencies. This tallies with the fact that persons who would at ordinary times
have left the country because of incipient phthisis were prevented from doing so by the war. Again, in
the years 1919,1920 and 1921, there was a marked fall in the numbers of female and male deaths at these
ages, owing in part to resumption of ocean traffic and the migration of persons with early phthisis
from this country. Turning now to ages over 50, in women the rise up to 1918, and the subsequent
decline, in the numbers of phthisis deaths were both much less marked than in the women 20-40.
As regards the men over 50, there was some increase in the deaths from 1914-18, and a decline since
1918, more marked than in the case of the women. The figures suggest that phthisical men at these
older ages were to some small extent held up in this country by the war, but that this was much less
marked in the case of women.
The London figures for male deaths 40-50, show less rise during the war years than those for men
over 50, but, of course, the class 40-50 would be more depleted for war service than the later ages. The
decline in phthisis deaths at 40-50 since 1918, is fairly well marked; men at this age have during the