8
Scientific Memoirs by
When cultivated in a temperature ranging between 16 and 21º C. in nutritive
beef-juice gelatine containing 10 per cent. of Heinrich's "gold-label" emulsion-
gelatine in vertical test tubes, visible growth, , and liquefaction of the basis is visible
within twenty-four hours, in the form of a small crater and short tapering funnel.
At the close of forty-eight hours the crater is enlarged, and the solution has
extended along the entire course of the track. The rate at which liquefaction
proceeds is more rapid than in cultivations of species, є, ζ, η and -ı, and slower
than in the case of cultivations of the remaining species. The solution at the
surface takes place slowly, as compared with that along the course of the needle-
track, so that the tube is relatively large in comparison to the orifice, and does
not taper so much as in the case of those in cultivations of some other species.
I have never observed the crater to include an air-bubble as described in the case
of gelatine cultivations of Koch's Comma.
When cultivated in 0.8 p e r c e n t . n e u t r a l i s e d A g a r - a g a r n u t r i t i v e g e l a t i n e
its growth is relatively slow. This appears specially distinctly in regard to the
surface growth in tube cultivations, in cases where the consistence of the basis is
dense, either as the result of low temperature, or of prolonged preservation and
consequent evaporation. The surface growth is relatively thin, perfectly smooth
and shining, and either diffluent, or at utmost slightly adhesive (vide Table I).
In plate-cultivations the colonies are relatively small, and the intersticial ones
of very dense texture, these characters coming out very distinctly when the
cultivations are viewed under low magnifying powers. When the basis has not
been neutralised, the growth is purely confined to the surface and takes place
very slowly—more slowly than in the case of any other species, and very much
more slowly than in any other species, save species y. In most cases no visible
sign of growth presents itself for several days, and then only as a very thin,
hardly recognisable film, which, especially at relatively low temperatures, in-
creases in thickness very slowly.
It is not at all easy to grow successfully on potatoes at any temperature, and
where success is attained it is apparently, as in other cases, owing to certain
peculiarities in the constitution of the potatoes, and not to the temperature to
which they may be exposed. Where growth occurs at all, it is in most cases of
limited extension, and only forms a thin, barely recognisable, transparent, color-
less or brownish film; but in one case (vide Plate II, Fig. I), after some time
localised thickenings occurred in this at certain points. These ultimately be-
came of firm consistence, of a greyish-white color, and with a wrinkled surface,
and consisted of dense zoogloeic masses, containing Commas of various sizes em-
bedded in a gelatinous, readily-staining basis. Tube cultivations of this mate-
rial in common Agar-agar basis gave characteristic pure cultivations of Commas
presenting all the distinctive features proper to the species.
When cultivated in neutral or teebly alkaline, peptonised broth, a relative
slowness of growth is sometimes very conspicuous, but not by any means with