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toms characterising these and cognate diseases; that
the same agent striking through the alimentary
canal may give rise to the symptoms of enteric fever,
cholera, and that group ; that the respiratory organs
acting as another channel may perhaps lead to the
phenomena that we express by the terms 'scarlatina,'
'measles,' &c.?" and that the hygienic and
other conditions under which the subject of infection
lives may also modify the results. Given, in fact,
a molecule of organic matter in a peculiar state of
motion or decay, and he believes, from the investigations
of Laplace, of Berthollet, and of Liebig, that
it will communicate its motion to other molecules of
matter which are susceptible of such motion, and thus
produce zymotic disease, so that ''A certain number,
of individuals subjected to the contagion of
these molecules in motion have the action extended
to their bodies, and diffuse the diseased action in a
constantly widening circle. And this very diffusion,
whilst extending the ravages, tends to limit the
duration, and gradually diminish the intensity of
the disease. As the undulations of ruffled water
gradually die away in the distance—as the waves of
sound decrease in intensity as they are diffused
through a larger space—as a heated substance gradually
imparts its motion to contiguous matter until
a condition of statis is arrived at, so this poisonous
action loses in intensity as it gains in extension,