he
anti-tetanic act by neutralising the specific toxins of the
disease--_antitoxic serums_; the anti-streptcoccic and the serum for
anthrax act upon the bacteria--_anti-bacterial serums_.

A _polyvalent_ serum, that is, one derived from an animal which has been
immunised by numerous strains of the organism derived from various
sources, is much more efficacious than when a single strain has been
used.

_Clinical Use of Serums._--Every precaution must be taken to prevent
organismal contamination of the serum or of the apparatus by means of
which it is injected. Syringes are so made that they can be sterilised
by boiling. The best situations for injection are under the skin of the
abdomen, the thorax, or the buttock, and the skin should be purified at
the seat of puncture. If the bulk of the full dose is large, it should
be divided and injected into different parts of the body, not more than
20 c.c. being injected at one place. The serum may be introduced
directly into a vein, or into the spinal canal, _e.g._ anti-tetanic
serum. The immunity produced by injections of antitoxic sera lasts only
for a comparatively short time, seldom longer than a few weeks.

_"Serum Disease" and Anaphylaxis._--It is to be borne in mind that some
patients exhibit a supersensitiveness with regard to protective sera, an
injection being followed in a few days by the appearance of an
urticarial or erythematous rash, pain and swelling of the joints, and a
variable degree of fever. These symptoms, to which the name _serum
disease_ is applied, usually disappear in the course of a few days.

The term _anaphylaxis_ is applied to an allied condition of
supersensitiveness which appears to be induced by the injection of
certain substances, including toxins and sera, that are capable of
acting as antigens. When a second injection is given after an interval
of some days, if anaphylaxis has been established by the first dose, the
patient suddenly manifests toxic symptoms of the nature of profound
shock which may even prove fatal. The conditions which render a person
liable to develop anaphylaxis and the mechanism by which it is
established are as yet imperfectly understood.

_Vaccine Treatment._--The vaccine treatment elaborated by A. E. Wright
consists in injecting, while the disease is still active, specially
prepared dead cultures of the causative organisms, and is based on the
fact that these "vaccines" render the bacteria in the tissues less able