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greater than was formerly the case, but the shifting would appear
to be somewhat greater in the case of Typhus and Typhoid Fevers
than in the case of small-pox.
The diminution of mortality of infants side by side with
increase of mortality of older persons, which has been claimed to
specially indicate the influence of vaccination upon small-pox
mortality, seems to be also true in a remarkable manner of
Influenza.
The Register-General, in his Fifty-fourth Report, institutes a
comparison between the great Influenza epidemics of 1847-48
and 1890-91, and calls attention to the fact that "the epidemic of
1890-91 was distinguished from the equally fatal epidemic of
1847-48 by the greater comparative severity with which it attacked
persons of middle age," and the table he gives shows that, while
at ages under fifteen there was a lower rate in the last epidemic,
at ages from fifteen to fifty-five there was an enhanced mortality,
while above sixty-five there was again a reduction.
We find in these facts evidence that in diseases other than
Small-Pox, and against which no artificial protective is invoked,
there has been a change in the age-incidence of deaths and deathrates
in the same direction as, and not very dissimilar in amount
from, that which has been asserted to be distinctive of small-pox
in consequence of the special influence of vaccination upon it.
We are bound to conclude that a theory of causation, which takes
no account of these phenomena, is unequal to an adequate
explanation of the whole case.
If we are right in our conclusion that causes other than
vaccination are operative upon the age-incidence of fatal smallpox,
and if, as we hold, sanitary measures are influential upon
small-pox mortality, and if it be true that "it is against noxious
influences to which the young are especially sensitive that the
weapons of sanitary reformers have been chiefly directed," we
should naturally expect to find that in sanitary or healthy districts