Medical Officers of the Army of India.
2I
as an average capacity, now present conspicuous differences, because in the
first a great increase, in the second a great decrease, and in the third no appre
–ciable modification in power has occurred. So, in the case of forms ι and λ, which .
at the outset were alike characterised by deficient power, modifications have
occurred, which in the former have led to very great increase and in the latter
to appreciable decrease in capacity. The entire series of illustrations shows
most clearly that the various choleraic bacilli are very subject to modification
of property under the influence of external conditions, but the modifications
which have actually occurred are not of a nature to lead to the belief that the
various forms are essentially identical in nature.
Continued cultivation in neutralised agar-agar media undoubtedly in most.
cases produces a like effect on choleraic comma-bacilli in diminishing or appa-
rently absolutely abolishing their capacity for growth on potatoes, but so long
as any power of healthy growth is retained, no prolongation of exposure to like
conditions causes the least assimilation in the characters of the resultant
growths. Continuous series of cultivations of forms β and E on potatoes were
successfully conducted for more than nine months in 189o-91. The growths
occurred on portions of the same tubers, and were exposed to precisely similar
external conditions, but, in spite of this, they remained persistently distinct, and
at the close of the period retained all the characteristic differences which they
had presented at its outset. There was absolutely no evidence of any tendency
towards the assimilation of either growth to its neighbour or towards the estab-
lishment of a new form of growth of intermediate habit. So, again, with forms λ
and ζ continuous cultivation on potatoes has not served in any way to diminish
the differences which the very first cultures exhibited (Plate IV, Figs. 9, 11).
Moreover, in the case of those forms in which continued cultivation in agar-agar
media does not affect the capacity for growth on potatoes the cultures which now
arise as the result of inoculation from the current series of agar-agar tube cultiva-
tions present all the distinctive characters which were present in the very first
potato-cultures of each form. For example, the form designated ξ in my previ-
ous paper, and form λ .
of the present one have throughout been consistently distin-
guished by the extreme readiness with which they grow luxuriantly on potatoes,
inoculations from the ordinary continuous series of agar-agar tube-cultures hardly.
ever failing to belfollowed by abundant growths, but these growths retain precisely
the characters which they originally presented, and are just as distinct from one
another now as they originally were although derived from series of agar-agar
cultures which have been continuously conducted in the case of 8 for three years
and-a-half and in that of λ for nineteen months. So, in the case of form ι in
which the capacity for growth on potatoes, although by no means so great or
constant as in the two previous forms, has been throughout retained without
sensible diminution, and rather apparently with a certain amount of increase, the
characters of the growths which have occurred have remained consistently alike