Medical Officers of the Army of India.
1 5
The growth in form γ, which originally presented no conspicuous differences
in habit from that in form β is now constantly distinguished from the latter
and from all the other forms which are at present under consideration by the
fact that it has to a great extent lost the power of free diffusion throughout the
substance of the medium. It is, however, in the case of forms ι and λ
that we find the most.conspicuous peculiarities of habit constantly present.
They resemble one another in certain respects in regard to the changes in colour
which their growth induces in the nutrient medium, the latter always remaining
pale as compared to the strong amber tint which it acquires after it has been
for some time occupied by any of the other forms. This peculiarity is most
strongly marked in the case of λ, in which the medium appears to become abso-
lutely paler in colour than it originally was, probably as the result of alterations
in refraction induced by its permeation by the bodies of the bacilli, but it is also
unequivocal and constant in the case of ι. Whilst resembling one another in this
respect the growths of the two forms are constantly strikingly different from
one another in others. In ι the surface-growth is normally evenly tuberculate
and of a warm ochreous tint whilst in λ it is perfectly smooth and chalky white
or somewhat greenish, and is, moreover, characterised by a strong, peculiar,
urinous or fishy odour quite distinct from that attending the growth in ι or any
of the other forms.
The phenomena which manifest themselves in connection with cultures in
non-neutralised agar-agar media are certainly no more in favour of the view
that all the forms of choleraic comma-bacilli are mere varieties than those
presenting themselves in cases where the media have been neutralised. On
the contrary, so far as certain forms are concerned, they afford additional evi-
dence of the presence of specific differences both as regards capacity for growth
and morphological properties. Had all the forms been mere varieties, there is
good reason to believe that long continued culture on neutralised agar-agar
media would have given rise to general assimilation of property as regards
capacity for growth in non-neutralised media, but this has been by no means
the case, for whilst certain forms constantly and certainly grow vigorously and
rapidly when introduced into such media, others as constantly and surely grow
with extreme slowness and reluctance, or even occasionally refuse to grow at
all. Taking this as a ground for classification, we can at once distinguish
two groups, the first including formsζ θ
a n d
ι ,
a n d c h a r a c t e r i s e d b y g r e a t
incapacity for growth in acid media, and the second containing all the remaining
forms. Minor variations in capacity for growth manifest themselves in connec-
tion with certain of the forms included in the latter group, but those in the
former one are uniformly and sharply defined from all the others by the extreme
slowness with which any development occurs and generally by the abortive
character of the elements present in the resultant growths. At a period at
which all the other forms have completely or almost completely covered the