338 PATHOGENIC BACTERIA.

much resembles cholera. It was first isolated by Heider
in 1892. In appearance it is rather delicate and decidedly
curved. It is often united in sigmoid and semicircular
forms, and exhibits long spirals in old cultures. It is
actively motile, each organism presenting a terminal
flagellum.

The growth upon gelatin plates is rapid. Small light-
gray colonies, resembling those of cholera, but exhibit-
ing a dentate margin, are observed. The growth in
gelatin punctures also much resembles cholera, and the
agar-agar growth can scarcely be distinguished from it.

The potato growth has a distinct yellowish-brown
color.

Milk is coagulated in three or four days.

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v^r's:^ &*?•'*•-

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vv;^j^.^y'

FlG. 93.—Spirillum Danubicus, from an agar-agar culture; x 1000 (Itzerott and

Niemann).

This spirillum does not produce indol.

Heider found the spirillum pathogenic for guinea-pigs.

Spirillum I. of Wernicke.—This organism is about
twice as large as the cholera spirillum, liquefies gelatin
more rapidly, produces indol, and is feebly pathogenic
for guinea-pigs.

Spirillum II. of Wernicke.—This spirillum is smaller
than the cholera spirillum, liquefies gelatin more slowly,