and tar-like. The most notable feature,
however, in the majority of cases is the enormous enlargement of the
spleen, which is engorged with blood to such an extent that it often
ruptures, while its tissue is changed into a violet or black fluid mass.

The bacillus of anthrax, under certain conditions, retains its vitality
for a long time, and rapidly grows when it finds a suitable field in
which to develop, its mode of multiplication being by scission and the
formation of spores, and depending, to a great extent at least, on the
presence of oxygen. The morbid action of the bacillus is indeed said to
be due to its affinity for oxygen; by depriving the red corpuscles of
the blood of that most essential gas, it renders the vital fluid unfit
to sustain life. Albert Hoffa and others assert that the fatal lesions
are produced by the poisonous action of the toxins formed by the bacilli
and not by the blocking up of the minute blood-vessels, or the
abstraction of oxygen from the blood by the bacilli.

It was by the cultivation of this micro-organism, or attenuation of the
virus, that Pasteur was enabled to produce a prophylactic remedy for
anthrax. His discovery was first made with regard to the cholera of
fowls, a most destructive disorder which annually carries off great
numbers of poultry. Pasteur produced his inoculation material by the
cultivation of the bacilli at a temperature of 42 deg. C. in oxygen. Two
vaccines are required. The first or weak vaccine is obtained by
incubating a bouillon culture for twenty-four days at 42 deg. C., and
the second or less attenuated vaccine by incubating a bouillon culture,
at the same temperature, for twelve days. Pasteur's method of protective
inoculation comprises two inoculations with an interval of twelve days
between them. Immunity, established in about fifteen days after the
injection of the second vaccine, lasts from nine months to a year.

Toussaint had, previous to Pasteur, attenuated the virus of anthrax by
the action of heat; and Chauveau subsequently corroborated by numerous
experiments the value of Toussaint's method, demonstrating that,
according to the degree of heat to which the virus is subjected, so is
its inocuousness when transferred to a healthy creature. In outbreaks of
anthrax on farms where many animals are exposed to infection immediate
temporary protection can be conferred by the injection of anthrax serum.

_Human Beings._--For many years cases of sudden dea