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12
and the subsequent renewed decline following upon the war: these three were
shown to have been associated with to and fro shifting of maximum age incidence—
first (up to 1912-14) from young adults to middle life, second (during the war years)
from middle life back to young adults, and then in 1919 and 1920 there was some
indication of a tendency to decline at the young adult ages again. This reverting
process has not, however, been followed up since 1920, for, as has been seen, there
has been an increase of incidence upon young adult females (15-25) in 1921 and
1922 as compared with 1919 and 1920.
The conclusion drawn last year, from the behaviour of the rates in 1919, 1920
and 1921, that a renewal of the outward flow of population from this country, following
upon the re-establishment, of peace conditions, had led to a fall in the death rates
from phthisis at ages 15-25 in the three post-war years, has thus not been emphasised
by a further fall in the rate at ages 15-25 in 1922. Two considerations need, however,
to be borne in mind with regard to last year's phthisis rate at the ages specified.
First, there was considerable mortality from influenza in the early months of 1922,
and this led to a decided increase in the phthisis death-rate at advanced ages and
to some increase among women at the ages 15-25 from influenza ; the phenomenon
was in fact a repetition of one which occurred on a considerably greater scale in
1918. Secondly, the selection for treatment in sanatoria in this country of early
cases of phthisis, especially among young adults, has been more effectually accomplished
in recent than had been the case in earlier years ; and this has led to a certain
number of young adult women undergoing treatment here, and not going abroad
to the extent that occurred in earlier years. It appears, therefore, that, as was
observed more than a year ago by Dr. Stevenson, " the transfer in 1916 of the
maximum mortality of women from ages 35-45 (as in the preceding quarter century)
to 20-25, or even earlier to 15-20 in 1917, has now been maintained for five (now six
years) and the excess at 20-25 is so definite that it seems likely to continue for some
considerable time longer. This is a very marked and sudden change in a feature
of the disease which appeared to be stable, and to which much significance had
been attached; and it will be of interest when the new census results are available
to ascertain its distribution throughout those parts of the country hitherto characterised
by early and late mortality, and to find whether the movement is shared
by the other sex." A further point to be noted is the fact that the phthisis deathrates
of 1920, the year which followed upon the heavy influenza years of 1918 and
1919, were abnormally low, owing in part no doubt to the large number of phthisical
persons who had died as the result of attack by influenza in the two preceding years,
The increased phthisis rates in 1922 (and in less degree in 1921) may be attributed
to return, after experiencing the exceptionally low rates obtaining in 1920, to more
normal conditions.
The influence of migration was (as briefly noted in last year's report) carefully
considered by Dr. Greenwood in his Milroy Lectures on the Influence of Industrial
Employment upon General Health. Dr. Greenwood refers to my paper of 1912
(Proc. Roy. Soc. Med.) and to the Annual Report for 1920 (vol. III., p. 13). He
enquires whether the scale of internal migration of young adults " is large enough
to make any supposed effect upon the health of migrants a substantial factor of
mortality." He concludes, "Dr. Hamer is almost certainly correct in supposing
there to be ample material for the revelation of effects." He agrees, moreover,
that there is a townward trend of immigration at later ages of life, but that the
quality of the immigrants is different. "In adolescence and young manhood it
is a migration of the vigorous and hopeful; at later years it tends to be a migration
of those broken in the struggle for life, seeking, not perhaps with much hope, what
has hitherto escaped them. The immigration of the young and healthy lowers,
the immigration of the middle-aged and unhealthy increases, the urban death-rate."
He then suggests "that the change of environment from town to country may
have an extremely unfavourable effect upon the immigrants," and he refers to the
"considerable literature which has arisen of recent years around the question of