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CHOLERA.                                317

In size, and attain a peculiar transparent character which
is suggestive of powdered glass. The commencement
of liquefaction causes the colony to be surrounded with a
transparent halo. When this occurs the colony begins to
sink, from the digestion and evaporation of the medium,
and also to take on a peculiar rosy color.

In puncture-cultures in gelatin the growth is again so
characteristic that it is quite diagnostic (Fig. 83).    The

110.83.—Spirillum  cholera Asiatica;  gelatin puncture-cultures   aged  forty-
eight and sixty hours (Shakespeare).

growth takes place along the entire puncture, but devel-
ops best at the surface, where it is in contact with the
atmosphere. An almost immediate liquefaction of the
medium begins, and, keeping pace with the rapidity of
the growth, is more marked at the surface than lower
down. The result of this is the occurrence of a short,
rather wide funnel at the top of the puncture. As the
growth continues evaporation of the medium takes place
slowly, so that the liquefied gelatin is lower than the
solid surrounding portions, and appears to be surmounted
by an air-bubble.