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Scientific Memoirs by
disease, and I believe that his original theory only requires very trivial modifica-
tion to adapt it to the requirements of the increased information which has
been accumulated since he first propounded it. The modification lies merely
in ceasing to regard the bodies of the sick, as in any sense specially related to
the manufacture of the essential cause of the disease, as in any sense forming
an essential site for the manufacture and multiplication of the specific poison
which induces the characteristic phenomena of cholera. According to
Professor von Pettenkofer's theory the bodies of the sick were not the site for
the manufacture of the poison in elaborated and efficient form, but they had
a certain special relation to its manufacture, in that they constituted a special
site for the multiplication of the organisms which subsequently, if they encoun-
tered favourable conditions in the environment after leaving the site of their
original development, were capable of giving rise to the specific poison. The
bodies of the sick, therefore, were a potential, although not an actual, site of
manufacture of the latter. But there is really no satisfactory evidence of
the existence of any such potential manufacture. It was apparently only to
account for the unquestionable influence that human intercourse exerts in
promoting the diffusion of the disease that the assumption of its existence
was introduced into the theory, and in the light of our present knowledge it
appears that its introduction is not only entirely unnecessary but calculated
to lead to complication. If the elaboration of the specific cause of the disease
be due, as there seems to be little doubt that it actually is, to the action of
schizomycete organisms, and if this action be carried on in the environment and
dependent on the presence of certain conditions there,there is no sufficient ground
for assuming that the human organism is in any way necessarily related to it, save
as a subject on which it can act. The manufacture of the poison according to
the theory implies the existence of certain conditions in a locality and the
presence of certain organisms which may either be a normal inmate of it, or
may have to be introduced into it, but there is no logical necessity for
supposing that introduction must necessarily be effected by means of the
intestinal discharges of those who have come from a previously infected
locality, and subsequently develop the symptoms of the disease. People surely
carry other things with them beyond the contents of their intestinal tract
when they move from one locality to another, and, granted that local conditions
are favourable, the introduction of very minute quantities of the organisms on
whose presence the elaboration of the poison appears to be dependent will
amply suffice to secure the rapid local formation of the latter in very large
amount. It may be asked why it is that the importation of the disease is ap-
parently so much more frequently connected with the advent of individuals who
are either on arrival already ill, or who subsequently are attacked by cholera, than
with that of those who, equally coming from an affected side, show no symptoms
of disease, but it is not hard to find an explanation of this without assuming
3 )A