Medical Officers of the Army of India.
The orifice of the tube is sharply defined and abrupt and is plugged below
by a conspicuous white mass of growth. Above this it is usually empty of
fluid, and hence the peculiar appearances due to the presence of air in it are
frequently very conspicuous. The lower part of the tube, due to its narrow lumen,
is usually very conspicuous as a white streak of accumulated deposit. Gelatine
cultivations of a few days' growth are also distinguished from corresponding cul
- t i v a t i o n s o f a n y o f t h e o t h e r s p e c i e s , b y s h o w i n g m u c h m o r e d i s t i n c t p u r p l e o n
the addition of acids than they do, and by there being hardly any tendency to
the development of any yellow color.
Growth occurs rapidly in neutralised Agar-agar media both superficially
and intersticially. The intersticial growth has, however, in the early periods
of cultivation, a marked tendency to be limited to the upper portion of the
course of the needle-track. This is especially marked when the cultivations
are exposed to relatively low temperatures, so that, at temperatures ranging
between 16° and 21º C., the intersticial growth at the close of the first twenty-four
hours usually presents the form of a short, conical cloud not extending beyond the
upper fourth of the track. The superficial growth ultimately forms a thick,
soft, perfectly diffluent and very opaque stratum, which never shows any trace
of adhesiveness. Cultivations of a few days' duration also show another dis
- t i n c t i v e f e a t u r e i n t h e f o r m o f a d i f f u s e o l i v e d i s c o l o r a t i o n o f t h e s u b s t a n c e o f
the medium, very unlike the yellow tint present in it in the case of cultivations
of all the other species capable of intersticial growth, and which goes on and
increases in degree as time advances. The colonies in Agar-agar plates pre
- s e n t c e r t a i n v e r y c h a r a c t e r i s t i c a p p e a r a n c e s i n m o s t c a s e s . T h e y h a v e a v e r y
distinct, dense nucleus, surrounded by a softer peripheral area, which is at first
coarsely granular and afterwards becomes covered with projecting nodular
elevations so that the entire surface is coarsely tuberculate.
When non-neutralised Agar-agar is substituted, growth manifests itself com-
paratively early, a limited white patch usually being recognisable around the orifice
of the needle-track within twenty-four hours after inoculation. The extension
over the surface is, however, very slow and irregular, and the patch, although of
some thickness, remains for long of very small area and with an irregular out
- l i n e . C u r i o u s l y e n o u g h , w h i l s t t h i s i s t h e c a s e , i n t e r s t i c i a l g r o w t h o c c u r s m u c h
more conspicuously than in the case of corresponding cultivations of any other
species, and the entire course of the needle-track becomes surrounded by an
irregular dense cloud of growth.
Growth on potatoes does not occur readily. In successful cases it pre
- s e n t s i t s e l f i n t h e f o r m o f t h i n , m o i s t e x p a n s i o n s o f a s t r o n g I n d i a n y e l l o w c o l o r ,
consisting of very minute, short, thick, often distinctly vacuolate Commas, which
are not readily induced to grow when transferred to other potatoes.
Cultivations in broth present equally conspicuous distinctive features.
Clouding of the fluid takes place slowly, only a very light cloud being present at
E 2
27