he
fully-developed spores, and posed the substance to a variety of
conditions. He permitted the dried blood to assume the form of dust;
wetted this dust, allowed it to dry again, permitted it to remain for
an indefinite time in the midst of putrefying matter, and subjected it
to various other tests. After keeping the spore-charged blood which
had been treated in this fashion for four years, he inoculated a
number of mice with it, and found its action as fatal as that of blood
fresh from the veins of an animal suffering from splenic fever. There
was no single escape from death after inoculation by this deadly
_contagium_. Uncounted millions of these spores are developed in the
body of every animal which has died of splenic fever, and every spore
of these millions is competent to produce the disease. The name of
this formidable parasite is Bacillus anthracis. [Footnote: Koch found
that to produce its characteristic effects the _contagium_ of splenic
fever must enter the blood; the virulently festive spleen of a
diseased animal may be eaten with impunity by mice. On the other
hand, the disease refuses to be communicated by inoculation to dogs,
partridges, or sparrows. In their blood Bacillus anthracis ceases to
act as a ferment. Pasteur announced more than six years ago the
propagation of the vibrios of the silkworm disease called _flacherie_,
both by fission and by spores. He also made some remarkable
experiments on the permanence of the _contagium_ in the form of spores.
See 'Etudes sur la Maladie des Vers a Soie,' pp. 168 and 256.]

Now the very first step towards the extirpation of these _contagia_ is
the knowledge of their nature; and the knowledge brought to us by Dr.
Koch will render as certain the stamping out of splenic fever as the
stoppage of the plague of _pebrine_ by the researches of Pasteur.
[Footnote: Surmising that the immunity enjoyed by birds might arise
from the heat of their blood, which destroyed the bacillus, Pasteur
lowered their temperature artificially, inoculated them, and killed
them. He also raised the temperature of guinea-pigs after
inoculation, and saved them. It is needless to dwell for a moment on
the importance of this experiment.] One small item of statistics
will show what this implies. In the single district of Novgorod in
Russia, between the years 1867 and 1870, over fifty-six thousand cases
of death by splenic fever, among horses, cows, and sheep were
recorded. Nor did