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It has been found that scarlet fever convalescents give a
negative reaction and that when the test is applied to large numbers
of persons about 41.6 give positive reactions.
Zingher found that in testing 4,570 normal persons of all
ages the maximum number of positive reactions was found in
infancy and decreased with advancing age as with the Schick test.
Zingher believes that a strongly positive Dick test in a case diagnosed
as scarlet fever of several days duration casts considerable doubt on
the diagnosis. In the first few days of an attack of Scarlet fever
the reaction is positive but later becomes negative.
Okell and Parish found that of those with a history of scarlet
fever 65% gave a Dick positive reaction, and recent convalescents
18%.
Kerr, McCartney and McGarrity got 51.5% positives in 442
persons not suffering from scarlet fever and 79% negatives in scarlet
fever patients on the 40th day of the illness.
Immunization.—It has been found that the injection of the
toxin into horses and sheep produces an anti-toxin which has
curative effects on scarlet fever patients. This anti-toxin serum
gives the Schulz-Charlton reaction in cases of scarlet fever. Further,
the Dicks have tried to immunize a large number of susceptibles by
injecting small definite doses of toxin on three occasions at 5 day
intervals with apparently successful results.
The whole question of the standardisation of the test and of
specific active immunization is still being followed up by numerous
experimenters in America, in this country and elsewhere so that
before many years pass we shall have the Dick test so perfected
as to be as trustworthy as the Schick test and that we shall be
provided with a satisfactory means of immunizing susceptibles
against scarlet fever as against diphtheria. In America the Dick
test is being applied with the same enthusiasm as the Schick test,
so that we can expect many reports of progress in the early future,