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322 PA THOGENIC BACTERIA.
matic. Pettenkoffer's theory is that the disease has
much to do with the ground-water and its drying zone.
He regards as the principal cause of the disease the de-
velopment of germs in the subsoil moisture during the
warm months, and their impregnation of the atmosphere
as a miasm to be inhaled, instead of ingested with food
and drink. This idea of Pettenkoffer's, combined with
his other idea that individual predisposition must pre-
cede the inception of the disease, is scarcely compatible
with what has gone before, and cannot possibly be made
to explain the march of the disease from place to place
with caravans, or its distribution over extended areas
when fairs and religious gatherings among the Hindoos
break up, the people from an infected centre carrying
cholera with them to their homes.
While it is an organism that multiplies with great
rapidity under proper conditions, the cholera spirillum
is not possessed of much resisting power. Sternberg
found that it was killed by exposure to a temperature
of 52° C. for four minutes.' Kitasato, however, found
that ten or fifteen minutes' exposure to a temperature
of 55° C. was not always fatal. In the moist con-
dition the organism may retain its vitality for months,
but it is very quickly destroyed by desiccation, as was
found by Koch, who observed that when dried in a thin
film its power to grow was destroyed in a few hours.
Kitasato found that upon silk threads the vitality might
be retained longer. Abel and Claussen have shown that
it does not live longer than twenty to thirty days in fecal
matter, and often disappears in one to three days. The
organism is very susceptible to the influence of carbolic
acid, bichlorid of mercury, and other germicides.
The organism is also destroyed by acids. Hashimoto
found that it could not live longer than fifteen minutes
in vinegar containing 2.2-3.2 per cent, of acetic acid.
This low vital resistance of the microbe is very fortu-
nate, for it enables us to establish safeguards for the pre-
vention of the spread of the disease. Excreta, soiled