468	.         PATHOGENIC BACTERIA.
thin, moist, grayish-white growth takes place upon the
surface of the potato.
The vital resistance of the organism is not great. Its
thermal death-point was found to be 58° C. after ten
minutes' exposure. Cultures made by displacing the air
with hydrogen are less vigorous than those in which the
oxygen is absorbed from the air by pyrogallic acid. It
was found that in the former class of cultures the bacillus
generally died in three days, while in the absorption ex-
periments it was kept alive at the body-temperature for
one hundred and twenty-three days. It is said to live
longer in plain than in sugar-agar. To keep the cultures
alive it has been recommended to seal the agar-agar tube
after two or three days' growth.
It is believed that the natural habitat of the bacterium
is the soil, but there is reason to think that it occurs in
the intestine at times, and it may occasionally be found
upon the skin.
The pathogenic powers of the bacillus are limited, and
while in some cases it seems to be the cause of a fatal
outcome in infected cases, its power to do mischief in the
body seems to depend upon the pre-existence of other
depressing and devitalizing conditions predisposing to its
growth.
Being anaerobic, the bacilli are unable to live in the
circulating blood, but they grow in old clots and in cav-
ities, such as the uterus, etc., where but little oxygen
ever enters, and from such areas enter the blood and are
distributed.
In support of these views Welch and Nuttall cite the
result of inoculation into healthy and diseased rabbits.
When a healthy rabbit is injected with 2^/2 c.cm. of a
fresh sugar-bouillon into the ear-vein it generally recov-
ers without any evident symptoms. One of their rabbits
was pregnant, and at time of injection was carrying two
dead embryos. After similar injection with but i c.cm.
of the culture it died in twenty-one hours. It seems that
the bacilli were first able to secure a foothold in the dead