Chapter IX

THE MECHANISM OF ACQUIRED IMMUNITY AGAINST MICRO-ORGANISMS 250
Cytases and fixatives.—Only the latter are augmented in the
immunised organism.—Properties of the fixatives.—Difference
between them and the agglutinative substances.—The part played
by the latter in acquired immunity.—Protective property of the
fluids of the immunised organism.—Stimulant action of the body
fluids.—The protective power of serum cannot serve as a measure
of acquired immunity.—Examples of acquired immunity in which the
serums exhibit no protective power.—Phagocytosis in acquired
immunity.—Negative chemiotaxis of leucocytes.—Theory of
attenuation of micro-organisms by the fluids of immunised
animals.—Refutation of this theory.—Phagocytosis acts without
requiring any previous neutralisation of the toxins.—The origin
of the fixative and protective properties of the body
fluids.—The relation between these properties and
phagocytosis.—The side-chain theory of Ehrlich and the theory of
phagocytes.

CHAPTER X

RAPID AND TEMPORARY IMMUNITY AGAINST MICRO-ORGANISMS, CONFERRED BY
SPECIFIC AND NORMAL SERUMS, OR BY OTHER SUBSTANCES, OR BY
MICRO-ORGANISMS OTHER THAN THOSE AGAINST WHICH IT IS DESIRED TO
PROTECT AN ANIMAL 300
Immunity conferred by specific serums.—Analogy of the mechanism of
this immunity with that observed in immunity obtained with
pathogenic micro-organisms and their products.—Part played by
phagocytosis in the immunity conferred by specific
serums.—Influence of opium on the course of immunisation by
these serums.—Stimulant action of specific serums.—Protective
and stimulant action of normal serums.—Influence of fluids,
other than serums: broth, urine, physiological saline solution,
etc.
Antagonism between anthrax and certain bacteria.

CHAPTER XI

NATURAL IMMUNITY AGAINST TOXINS 325
Examples of natural immunity against toxins.—Immunity of spiders
and scorpions against tetanus toxin.—Immunity of the scorpion
against its own poison.—Antivenomous property of the blood of
the scorpion.—Immunity against tetanus toxin in the larvae of
_Oryctes_ and in the cricket.—Immunity and susceptibility of
frogs against this toxin.—Natural immunity of reptiles against
tetanus toxin.—Antitetanic property of the blood of
alligators.—Immunity of snakes against snake venom.—Immunity of
the fowl against tetanus toxin.—Immunity of the hedgehog against
poisons and venoms.—Immunity of the rat against diphtheria
toxin.