Scientific Memoirs by
case of forms ζ, θ and ι. Form ν presents exceptional phenomena in that
incertain cultures growth takes place rapidly and without any considerable
modification, whilst in others it is, primarily at all events, greatly retarded and
attended by substitution of coccoid for bacillar elements. This variability is
presumably related to the presence of minor differences in the constitution of the
medium, but hitherto it has not been possible to recognise definitely what these
are. The effect of such minor differences also appears conspicuously in
connection with form ι which refuses to grow at all in certain samples of non-
neutralised media in which even ζ a n d
θ p r o d u c e t h e i r n o r m a l l y r e t a r d e d g r o w t h s .
In this case it appears possible that density of the substratum is the effective
agent in preventing growth, as in certain cases in which growth occurred in
tubes containing portions of a sample of the medium shortly after its prepara-
tion and whilst it was still relatively soft, no result followed inoculation of other
tubes of the same series after an interval in which their contents had acquired
increased density in consequence of continued evaporation.
When we come to consider the characters of the,growths which the various
forms of choleraic bacilli now yield in common gelatine media, we find equally
little evidence of any general assimilation in their properties as the result of
continuous exposure to like, common conditions. In certain cases undoubted-
ly the differences primarily present have undergone diminution, but these are
more than counterbalanced by a series of other cases in which an increase in
place of a decrease in dissimilarity has occurred. A glance at the photographs
in Plate I is enough to show that no general assimilation has occurred in respect
to liquefactive property, and a study of the figures in the two following plates
demonstrates that the essential differences in property indicated by the photo-
graphs are now permanent and not to be accounted for as the result of any acci-
dental peculiarities in the series of tubes which were photographed.
The figures in Plate I consist of photographs of tube-cultures of thirteen
distinct forms of comma-bacilli obtained from cases of cholera and of one of
non-choleraic origin. Of the choleraic bacilli nine are forms which have been
already described in my previous paper on this subject, and four are new ones
which have been obtained since its publication. At the time at which the cul-
tivations which are here illustrated were carried out forms α, β and γ had been
in continuous cultivation in agar-agar media for rather more than three years,
forms ε, ζ and 0 for two years and a half, forms ι a n d
κ f o r t w o y e a r s a n d
one month, λ and μ for one year and two months, and forms ν and ζ f o r a b o u t t e n
months. The tubes which are figured all belonged to a single series of cultures
derived from a single series of agar-agar tubes, and the gelatine medium which
they contained consisted of portions of one and the same sample of beef-
juice gelatine. They were all inoculated on the same day, they were exposed to
precisely the same external conditions, and the photographs were all taken on
the same morning, five days after the date of inoculation. In the lower part of
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