TETANUS. 277

an atmosphere of hydrogen upon gelatin plates, somewhat
resemble those of the well-known hay bacillus. There
is a dense rather opaque central mass from which a more
transparent zone is readily separable. The margins of
this outer zone are made up of a radiating fringe of pro-
jecting bacilli (Fig. 75). The liquefaction that occurs is
much slower than that caused by bacillus subtilis.

When grown in gelatin puncture-cultures the develop-
ment occurs deep in the puncture, and consists of mul-
titudes of short-pointed processes radiating from the
puncture, somewhat resembling a fir tree (Fig. 73).
Liquefaction begins in the second week and causes the
disappearance of the radiating processes. The liquefac-
tion spreads slowly, but may involve the entire mass of
gelatin and resolve it into a grayish-white syrupy liquid,
at the bottom of which the bacilli accumulate. The
growth in gelatin containing glucose is much more rapid ;
that in agar-agar punctures is much slower, but similar
to the gelatin cultures except for the absence of liquefac-
tion. The organism can also be grown in bouillon, and
attains its maximum development at a temperature of
37° C. Much gas is given off from the cultures.

Cultures of the tetanus bacillus in all media give off
a peculiar characteristic odor—a burnt-onion smell, with
a suggestion of putrefaction about it.

The methods for excluding the oxygen from the cul-
tures and replacing it by hydrogen, as well as other
methods suggested for the cultivation of the strictly
anaerobic organisms, are given under the appropriate
heading (Anaerobic Cultures), and need not be repeated
here.

A very simple method of cultivating the .bacillus in
bouillon for the purpose of securing a large amount of
toxin has been suggested by the author.1 An ordinary
bottle is filled with bouillon to the mouth, and closed
by a perforated rubber stopper containing a glass tube

1 Centralbl. f. Bakt. M. Parasitenk., xix., Nos. 14 and 15, April 25, 1896, p.
550-