Medical Officers of the Army of India.
17
in non-neutralised agar-agar media we might well be inclined to believe that
no such differences were present. In organisms so susceptible to modifica-
tion under the influence of alterations in environment as schizomycetes are
we may reduce or abolish the distinctive peculiarities which they normally
present by means of exposing them to the action of such uncongenial media
that they are incapable of producing any but abortive elements, but this is no
sufficient evidence that the normal differences are not of specific value. Could
it be shown that the resemblance thus produced were persistent when the organ-
isms were once more exposed to favourable conditions the phenomena would
certainly be in favour of an absence of specific differences, but as this is not the
case, and the resumption of vigorous growth is accompanied by the re-appear-
ance of the normal distinctive peculiarities, the evidence unequivocally points
in the opposite direction, as it shows that in spite of the great modifications
which have arisen under the influence of an unfavourable environment no general
assimilation in nature has been achieved.
Whilst the three forms ζ, θ and ι a r e c o n s p i c u o u s l y d i s t i n g u i s h e d f r o m a l l
the others by their relative incapacity for growth in non-neutralised agar-agar
media, form λ is almost as much distinguished by the readiness with which it
adapts itself to them, for not only does it spread over the surface , of the
medium with exceptional activity, but it alone is capable of giving rise to appre-
ciable growth within its substance, along the course of the track of the needle
in a stable-culture. Running parallel with this exceptional capacity for growth it
also shows very little tendency to appreciable modification of the morphologi-
cal characters of the elements developed in acid media. These never show any
conspicuous tendency to abbreviation or to the assumption of abortive or
involuted characters, but continue to appear as well formed bacilli, which only
differ from those developed in cultures on neutralised media in presenting even
less tendency to distinct curvature than the latter do (Plate IV, Fig. 7).
The degree of morphological modification exhibited by the other forms
Which grow readily on non-neutralised media varies very considerably. For
example the elements of forms α, β, ε, η and μ show very little modification beyond
a slight degree of shortening, whilst those of γ and ξ are ordinarily modified
almost beyond recognition. The modification in the case of γ is, as has been
previously mentioned, of such a nature as to cause the elements to assume the
characters of those proper to form β, whilst in the case of ξ even greater alteration
takes place, so that very few recognisable comma-bacilli can be recognised, and
by far the greater bulk of the elements present the form of oval cocci, solitary
or associated in pairs, so that a cover-glass preparation comes very closely to
resemble one derived from many of the cultivations of the same form in potatoes.
With regard to rate of growth there is little difference to be recognised between
the various members of this group of forms, save that in the case of ε and η it
is appreciably retarded although the delay does not approach that present in the
D