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breaks of diphtheria. The protection is particularly desirable in
the administrative staffs of our isolation hospital. The nurses at
the Chiswick and Pealing Isolation Hospital are protected in this way.
Parents may, when they know of the procedure, very laudably
wish their children protected, particularly when they leave home
for a boarding school or when alarm is caused by the presence of
diphtheria in the neighbourhood. In these circumstances the
family medical attendant should be prepared to carry out the Schick
test or at least to perform artificial immunization.
Scarlet Fever.—As to scarlet fever, experiments have, since the
discovery of the causal organism in 1923 by Drs. George and Gladys
Dick, rapidly followed on similar lines to those regarding diphtheria.
Previous to that date it had been known that the blood serum of a
scarlet fever convalescent would cause, when injected into the skin,
blanching of the rash, round about the site of injection, in a patient
in the acute stage of the disease. This test known as the SchulzCharlton
test was shown to be specific and to be a valuable means
of diagnosis in doubtful cases of scarlatiniform rash. After the
discovery of the streptococcus of scarlet fever by Dr. and Mrs.
Dick, who successfully produced scarlet fever in human volunteers
by infecting the nasopharynx with a culture, steps were taken to
produce a test similar to the Schick test in order to discover susceptibles
and non-susceptibles to scarlet fever. This test, known as the
Dick test, has been shown, first by Zingher in New York and
afterwards by others in America and in this country to be almost
as satisfactory for its purpose as the Schick test in diphtheria.
The Dick Test.—The Dick test consists in the injection into
the skin of a small quantity of the diluted toxin. A positive
reaction indicates that the individual is presumably susceptible
to scarlet fever while a negative reaction yields evidence that the
individual is immune to the disease. A positive reaction begins
to appear within a few hours, usually four to six after inoculation
and reaches its maximal development in about 24 hours. There is
a local area of redness varying in size and in intensity of colour,
with usually clearly defined edges. At the expiration of 48 hours
from the time of injection in most cases the reaction has completely
disappeared or has faded considerably.