IMMUNITY AND SUSCEPTIBILITY. 75

Wyssokowitsch found them most numerous in the liver,
spleen, and bone-marrow, and found that in these situa-
tions they were destroyed in a short time—saprophytic
in a few hours, pathogenic in from twenty-four to forty-
eight hours. Spores of Bacillus subtilis remained as
living entities in the spleen for three months.

An interesting communication upon phagocytosis is
that of Bordet, whose experiments seem to show that the
lack of disposition to take up bacteria on the part of the
leucocytes may depend upon negative chemotaxis. He
found that when a guinea-pig became very ill after the
intraperitoneal introduction of a streptococcus of mild
virulence, if an injection of a culture of Proteus vulgaris
was given, the leucocytes, which had steadily refused to
take up the streptococci, seized upon the bacilli with
avidity. This seems to show that a chemical, or other
negative, or inhibitory influence felt by the leucocyte,
prevents it from taking up all the bacteria that come
within reach.

4. THE HUMORAL THEORY.—It was observed that if
anthrax bacilli were introduced into a few drops of
rabbit's blood, they were instantly killed. This obser-
vation was one of immense importance, and from it and
similar observations Buchner deduced the principles of
his theory, which teaches that the destruction of patho-
genic bacteria in the body is due to the bactericidal
action of the blood-plasma, not to phagocytosis, which
phenomenon amounts to nothing more than the burial
of the dead bacteria in £C cellular charnel-houses." The
experiments of Buchner and his followers, conspicuous
among whom is Nuttall, have shown that freshly drawn
blood, blood-plasma, defibrinated blood, aqueous humor,
tears, milk, urine, and saliva possess marked destructive
influence upon the organisms brought in contact with
them—an influence easily destroyed by heat.

The apparent paradox of rapid multiplication of an-
thrax bacilli in the rabbit's blood enclosed in the rabbit's
body, and the reversed action in the test-tube, caused im-