TETANUS, 279

contact with the soil, or enter abrasions from the soil
directly. Doubtless many of the wounds are so small
that their existence is overlooked, and this, together
with the fact that the period of incubation of the dis-
ease, especially in man, is of considerable duration, and
at times permits the wound to heal before any symptoms
of intoxication occur, serves to explain to us at least some
of the reported cases in which no wound is said to have
existed.

It would seem that in some rare cases tetanus can occur
without the previous existence of a wound. Such a case
has been reported by Kamen, who found that the intes-
tine of a person dead of the disease was rich in the
Bacillus tetani. Kamen is of the opinion that the
bacilli can grow in the intestine and be absorbed, espe-
cially where there are imperfections in the mucosa. It
is not impossible, though he does not think it probable,
that the bacteria growing in the intestine could elaborate
enough toxin to produce the disease by absorption.

All animals are not alike susceptible to the disease.
Men, horses, mice, rabbits, and guinea-pigs are all sus-
ceptible ; dogs are much less so. Most birds are scarcely
at all susceptible either to the bacilli or to the poison.
Amphibians are immune, though it is said that frogs
can be made susceptible by elevation of their body-
temperature.

When a white mouse is inoculated with an almost
infinitesimal amount of bouillon or solid culture, or is
inoculated with garden-earth containing the tetanus
bacillus, the disease is almost certain to follow, the
first symptoms coming on in from one to two days.
The mouse develops typical tetanic convulsions, which
begin first in the neighborhood of the inoculation, but
soon become general. Death follows sometimes in a
very few hours. In rabbits the period of incubation is
nearly two weeks, and in man may be three weeks.

The conditions in the animal body are not favorable
for the development of the bacilli, because of the free