Scientific Memoirs by
It need hardly be a matter of surprise that such modifications should be
capable of rapid development, and of quickly acquiring greater or less perma-
nence in schizomycete organisms: the rapidity must be considered in relation to
the rapidity with which generations of such organisms succeed one another, and,
therefore, to the brief period within which it is possible for hereditary peculiarities
to become persistent.
It now only remains briefly to consider what are the main points indicated
by the above data. In the outset it is clear that they show that Koch's theory
that cholera is primarily due to the access of a specific Comma-Bacillus to the
interior of the intestinal tract must be finally abandoned as inconsistent with
fact. Koch's Comma-Bacillus certainly does occur in association with cases of
cholera in Calcutta, but it is not the only species which does so, and, indeed, it
does not appear to occur by any means so frequently as the other species taken
as a group do; for, taking the sixteen cases of cholera from which Comma-
Bacilli were obtained during the course of the past year, we find that in four of
them only was the species which was present even doubtfully that described by
Koch. This species is that which is distinguished as a in the present paper, and
the doubt as to its identity with Koch's species rests mainly on the persistent
differences presented by the phenomena attending cultivations of it in gelatine
as compared with those described by Koch as attending corresponding culti-
vations. Granting the identity, however, we have four cases in which it was
present, against twelve in which it was replaced by totally distinct species.
More than this, there is not even conclusive evidence to show that it is
specially associated with the more severe and fatal forms of the disease, for the
total number of cases is so small that the fact that three out of the four cases
in which it occurred were fatal, whilst only eight out of the twelve associated
with the other species were so, cannot be taken as of conclusive value in this
respect. Knowing what we do of Koch's original statements regarding his
discovery, we can only regard them as indicative of his ignorance, at that time,
of the frequency with which vibrionic schizomycetes occur, so that, when he
detected them in choleraic materials, he was readily led to assume on insufficient
grounds that he was in all cases dealing with a single specific organism. It had
long been vaguely recognised that vibrionic schizomycetes abounded in choleraic
materials, and Koch's discovery was, in fact, merely an arbitrary selection of one
of these as the cause of the disease, elected because it happened to be present
in a limited number of cases which specially came under his observation.
The species of Comma-Bacillus described by Koch is, then, certainly not the
specific and sole cause of cholera, but this does not necessarily imply that it is not
causally related to the disease, as a member of a group of organisms capable of
manufacturing noxious products of a definite nature. There can be no doubt that
all save one of the species of Comma-Bacilli which have been described above
possess many common properties indicative of their holding a close relation to one
34