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75
where the sanitary conditions were widely different. Whatever
may have been the sanitary improvements during the first quarter
of this century in England and some other countries, there seems
no ground for supposing that throughout Western Europe the
period was marked by great changes in the direction of improved
sanitation. Indeed, in many countries, down to a recent period,
in some, it may perhaps be said, even to the present time,
insanitary conditions have continued to prevail.
There is no proof that sanitary improvements were the
main cause of the decline of Small.Pox under discussion. And
no adequate evidence is forthcoming to show to what extent such
improvements may be considered as a subsidiary cause.
The decline in question followed upon the introduction of
the practice of vaccination. The records of Western Europe and
the United States show that, in all places whence returns were
obtained, the introduction of vaccination was followed by a
decline of Small.Pox ; the decline becoming especially apparent
after the lapse of such time as may be supposed to be necessary
for the due spread of the practice.
Moreover, the spread of the practice and the decline of the
disease do not stand as two phenomena simply following the
same course, but without any tie joining the two. The experimental
evidence offered at the time, namely, that the class of
vaccinated persons did not take Small.Pox by way either of
exposure to natural contagion or of inoculation, as the unvaccinated
did, connects the two and points to the spread of the
practice as the cause of the decline.
It has been suggested that the decline was due to some
general unknown conditions, which have been spoken of as
'cosmic' or 'secular.' It has been urged that such general
' cosmic' conditions led, on the one hand, to the spread of
Small.Pox in Europe during the seventeenth and especially during
the eighteenth centuries, and, on the other hand, conversely to its