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456                 PA THOGENIC BA CTERIA.

Milk also seems to be a favorable culture-medium.
The development of the bacilli is unaccompanied by

The virulence of the organism is soon lost in all
culture-media, but it is said that the virulence of the
culture can be much increased by the addition to it of
20 per cent, of lactic acid.

When susceptible animals are inoculated with a minute
portion of a pure culture in a little subcutaneous pocket,
such as is described in connection with tetanus and
malignant edema, the bacilli proceed to grow, pro-
duce the well-known affection, and lead to a certainly
fatal outcome. Cows seem to be the most susceptible
animals, especially those between six months and four
years old; sheep and goats are also sometimes affected.
Curiously enough, animals that are immune to malig-
nant edema are seemingly more susceptible to Rausch-
brand. Of the laboratory animals, the guinea-pig is
most susceptible; swine, dogs, and rabbits are very
slightly susceptible; horses, goats, and birds are im-

The virulence of the bacillus is capable of ready
attenuation by exposure to heat, by previous exposure
of its spores to heat, or by drying combined with ex-
posure to increased temperature. The inoculation of
animals with the attenuated bacilli causes a very mild
affection, followed by complete immunity to the viru-
lent organisms. Upon this principle the "protective
vaccinationn is based. Kitt has, however, shown that
almost the same method as that employed by Pasteur
for vaccination, against rabies may be employed against
this bacillus, and that when muscular tissue from an
animal dead of the disease is dried at a temperature of
33-35° C., and then exposed for six hours to a tempe-
rature of ioo°-i04° C-> and a second portion is exposed
in the same manner to a temperature of 9O°-95° C., an
emulsion of this tissue in distilled water, salt-solution,
or bouillon, injected into the animals to be protected, will