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34
some years, and has been adopted by twelve Metropolitan
Boroughs. It is in general use in fever hospitals
in London for the purpose of preventing the members
of the staff from contracting diphtheria.
The procedure is as follows:—
1. The Schick test is done to determine whether
the person is susceptible to diphtheria. This consists of
an injection into the skin of the left forearm of a small
amount—about two drops—of standardised diphtheria
toxin (recently diluted). The injection is given by
means of a syringe with a very fine needle and is practically
painless. A control injection is given at the
same time into the skin of the right arm. This consists
of diphtheria toxin which has been heated to destroy
its activity.
If a positive reaction occurs at the spot where the
needle was inserted into the left arm, this indicates
that the person is susceptible to diphtheria and that
preventive treatment is necessary. A positive reaction
consists of redness and thickening of the skin over an
area of half to one inch in circumference and takes
place one to three days after the injection. The reaction
lasts seven to ten days and subsides gradually.
If no reaction occurs, the person is insusceptible
or immune to diphtheria and the preventive injections
are therefore unnecessary. In young children of preschool
age the preliminary Schick test is generally
omitted as it has been found that they are practically
all susceptible and it is unnecessary to test them all
individually. The preventive injections are therefore
given without the preliminary Schick test. After the
age of six, and in adults, the test is always done and
only those who react positively need be immunised.
2. The Preventive Injections.—In this country toxoidanti-toxin
mixture is generally used as its use is free
from risk, whereas several accidents have occurred when
the toxin-anti-toxin mixture has been employed.
Three injections of 1 c.c. of the mixture (about
seventeen drops) are given at weekly intervals under