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until the diseased action is too feeble to overcome
the resistance of healthy action, and a state of statis
(restoration of health in the individual, cessation of
the epidemic in the community) is the result." But
although the entire phenomena of zymotic diseases,
and especially the reproductive powers of them, are
hardly consonant with what we know of the physical
manifestations of molecular motion, yet there is
much about them, as for example, their modes of
attack, their periodicity, the regularity of their progress,
the order of their decline, and, above all, the
quantitative or complementary relations of them,
which point to a probable correlation of some kind.
But whether the relation is in the quality of the
contagion, or in the nature of the material upon
which it acts, or in the force which governs its
manifestations, is a problem for searching enquiry;
for at present no man can safely dogmatise on this
obscure subject, by saying that these diseases are
caused by matter in a peculiar state of motion, or by
living germs with their faculty of reproduction, or
by the so-called "zymotic principles" of the Registrar-General.
All that we can certainly say of these
maladies is, that, be their origin what it may, or
their correlation as close as can be, they are governed
by laws which are quite within the reach of human
investigation; and that although perhaps we shall
never be able to banish such diseases from the