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In short, the organism seems to be confined to the bubo until short-
ly before death, and it is only then that it gains an entrance into the
blood stream, and becomes rapidly and widely disseminated in the
tissues and in the excretions, which one so constantly sees dribbling
away on to the floors and bedding in moribund cases.
Hence, in the interests of the living, a strong argument can be
deduced for the compulsory removal even of these moribund cases.
INFECTIOUSNESS OF CONVALESCENT CASE.
Examination of blood, and pus from buboes which had opened
naturally or been incised, gave negative results, and it therefore seems
unlikely that the organism can be present in the excretions of such cases.
VITALITY.
As to the vitality of the germ under laboratory conditions, it was
found that cultures grown for 57 days in one tube, and then transplanted,
flourished, and were capable of producing fatal Plague in rats, although
the incubation period was much longer than for more recent growths.
INCUBATION   PERIOD.
The usual period in rats was found to be from two to three days.
In the above case the period was seven days. Rats kept in cages in which
inoculated rats had just died of Plague did not develop the disease.
All attempts to isolate the organism from the floors of infected
dwellings or soil gave negative result both by plate cultivation and
inoculation.
Bacilli, closely resembling it both microscopically and in their
growths, were found, but did not stand the final test.
Rats inoculated with polluted soil generally died, but not of Plague.
Examination of the organs reveals the fact that malignant oedema
is usually the cause of death.
If, however, Plague bacilli have been purposely added to the soil
used, the rat dies of a mixed infection; but the Plague bacilli can be readi-
ly isolated from the organs, because the bacillus of malignant oedema
dies out at once in ærobic cultivations and leaves the Plague pure.
This method, therefore, of detecting the germ in the soil seems a
promising one to pursue, provided always the real cause of death is
scientifically ascertained.
Experiments are also in progress to find out the vitality of the germ
in sterile and polluted soil respectively.