developments of tenacity of life and of vital power have been
comparatively rapid in their course when they have once commenced.
There is nothing discoverable to us that would lead to the conception
of a human civilisation extending back over two hundred generations;
and when in these generations we survey the actual effect of
civilisation, so fragmentary and overshadowed by persistent
barbarism, in influencing disease and mortality, we are reduced to the
observation of at most twelve generations, including our own, engaged,
indirectly or directly, in the work of sanitary progress. During
this comparatively brief period, the labour of which, until within a
century, has had no systematic direction, the changes for good that
have been effected are amongst the most startling of historical facts.
Pestilences which decimated populations, and which, like the great
plague of London, destroyed 7,165 people in a single week, have lost
their virulency; gaol fever has disappeared, and our gaols, once each
a plague-spot, have become, by a strange perversion of civilisation,
the health spots of, at least, one kingdom. The term, Black Death, is
heard no more; and ague, from which the London physician once made a
fortune, is now a rare tax even on the skill of the hardworked Union
Medical Officer.

From the study of the past we are warranted, then, in assuming that
civilisation, unaided by special scientific knowledge, reduces disease
and lessens mortality, and that the hope of doing still more by
systematic scientific art is fully justified.

I might hereupon proceed to my project straightway. I perceive,
however, that it may be urged, that as mere civilising influences can
of themselves effect so much, they might safely be left to themselves
to complete, through the necessity of their demands, the whole