IMMUNITY AND SUSCEPTIBILITY. Si

minority of scientists, that the antitoxin is the toxin in
a modified (oxidized?) form, and supports his view by
the fact that the antitoxins are specific for their respec-
tive toxins only, and by quoting the experiments of
Kondrevitsky, who, killing animals two hours after
an injection of toxin, found in the blood toxin alone;
killing later, found some antitoxin, and still later much
antitoxin.

The difference between this theory of neutralization
by antitoxins and Chaveau\s retention-hypothesis is quite
marked. The retention-theory teaches that a bacterium
leaves behind it a substance prejudicial to its future
growth in the economy—a distinct metabolic product.
The antitoxic theory shows the protective substance to
be a product not of bacterial growth, but of tissue-energy,
not depending upon the presence of the bacteria, but
upon the presence of a poison.

The antitoxins do not usually act harmfully upon the
bacteria, or preclude their growth in the animal body, but
prevent their pathogenesis by annulling their toxicity—
i. e., enabling the body-cells to endure the injury—and
^placing them in a position exactly parallel with 11011-
pathogenic bacteria.

Closely related to the antitoxins, if not-identical with
them, are certain substances of an anti-infectious nature
that can be generated in the blood of animals to which,
in the process of immunization, the bacteria, instead of
their poisons, have been administered. The anti-infec-
tious serums are protective against the bacterial infections,
but powerless against the toxins. They are the only
results of immunization against cholera and typhoid
fever. When antitoxic serums can be secured they are
of far greater importance, and should always be selected
for purposes of therapeutics.

The diseases which are at present controllable by anti-
. toxins are toxic diseases, caused by the entrance of toxin-
producing bacteria into the body. The growth of these
toxin-producers probably depends upon the inability of