e inoculated, but never do they
produce such an excavation with the bladder-like cavity on the surface.
Another peculiarity was the slowness with which the gelatine liquefied,
and the narrow limits of this liquefaction in the case of a gelatine disk.
Cultures of the comma bacillus were also made in agar-agar jelly, which is
not liquefied by them. On potato these bacilli grow like those of
glanders, forming a grayish-brown layer on the surface. The comma bacilli
thrive best at temperatures between 30 deg. and 40 deg. C., but they are not very
sensitive to low temperatures, their growth not being prevented until 17 deg.
or 16 deg. C. is reached. In this respect they agree with anthrax bacilli.
Koch made an experiment to ascertain whether a very low temperature not
merely checked development but killed them, and subjected the comma
bacilli to a temperature of 10 deg. C. They were then completely frozen, but
yet retained vitality, growing in gelatine afterward. Other experiments,
by excluding air from the gelatine cultures, or placing them under an
exhausted bell jar, or in an atmosphere of carbonic acid, went to prove
that they required air and oxygen for their growth; but the deprivation
did not kill them, since on removing them from these conditions they again
began to grow.
The growth of these bacilli is exceptionally rapid, quickly attaining its
height, and after a brief stationary period as quickly terminating. The
dying bacilli lose their shape, sometimes appearing shriveled, sometimes
swollen, and then staining very slightly or not at all. The special
features of their vegetation are best seen when substances which also
contain other forms of bacteria are taken--_e. g_., the intestinal
contents or choleraic evacuations mixed with moistened earth or linen and
kept damp. The comma bacilli in these conditions multiply with great
rapidity so as to far outnumber the other forms of bacteria, which at
first might have been in far greater abundance. This state of affairs does
not last long; in two or three days the comma bacilli began to die off,
and the other bacteria began to multiply. Precisely the same thing takes
place in the intestine, where, after the rapid initial vegetation is over,
and when exudation of blood occurs in the bowel, the comma bacilli
disappear and putrefactive bacteria predominate. Whether the occurrence of
putrefaction is inimical to the comma bacilli has not been proved, but
from analogy it is ve
|