Medical Officers of the Army of India.
7
disciples and refuse to recognise that any cases of disease are of a truly
choleraic nature, unless they are accompanied by the classical commas, a
procedure which, however it may serve to maintain the integrity of the theory,
is clearly of no practical import to the community at large. The question with
which we have to deal here is, How far do the distinct forms of comma-bacilli,
which undoubtedly both in Europe and India are present in connection with different
cases of the disease, show' differences of specific value ; or, in other words, how
far do we find them continuing to differ from one another under the influence
of prolonged exposure to the influence of like. conditions ? In considering
it, we have, in the first place, to endeavour to ascertain whether choleraic
comma-bacilli are liable to undergo modification under the influence of external
conditions, and, secondly, how far any modifications arising under. the influence
of prolonged exposure to like conditions tend to give rise to any general
assimilation in the characters of primarily differing forms.
The fact that many forms of choleraic comma-bacilli are extremely liable
to modifications in form and properties in connection with variations in the
nature of their environment must be familiar to any one who has had any
opportunity of continuously studying such organisms. At the same time we find
that very considerable differences are presented by different forms in regard to
their liability to undergo such modifications, certain of them being relatively
stable, and, consequently, showing little variation in any medium in which they
are capable of existing at all, whilst others show immediate and considerable
modifications under the influence of certain alterations in their environment.
In dealing with this question we necessarily encounter a great difficulty in
determining how far we are ever dealing with truly uniform conditions in con-
tinued series of cultivations. The majority of ordinary culture-media cannot
be said to present truly fixed characters. Taking ordinary bouillon or beef-
juice-gelatine we have no security that any two successive samples possess
truly identical properties. Even within the limits of a single sample differ-
ences may arise simply as the result of time. Evaporation or absorption of
water may gradually give rise to alterations in consistence, which we are apt
to neglect as trivial, but which, as experience shows, are quite sufficient in
certain cases to induce changes in the characters of the organisms which
are exposed to their influence. We are ordinarily inclined to assume that so
long as a culture medium is neutralised it is of little moment by what means we
effect the process, but even the employment of one alkaline re-agent in place of
another may sometimes be sufficient to give rise to modifications in the cha
racters of organisms cultivated in the neutralised media. At a period in the
course of the past year when certain forms of choleraic comma-bacilli were
constantly giving growths in agar-agar beef-juice media neutralised with carbo-
nate of soda, which were characterised on the surface of the substratum by
extreme adhesiveness or ropiness, a set of culture-tubes was prepared in which