The active immunization against scarlet fever by repeated injections at weekly intervals of scarlatinal streptococcus filtrate toxin as described by Dick and Dick1 has been reported by a number of observers. It is said that following such injections an immunity usually develops which lasts from several months to a year and a half or possibly longer. The assumption of immunity is based not only on a decreased incidence of clinical scarlet fever in such injected persons, but chiefly on the fact that the reaction to the Dick test, or skin sensitivity to a small amount of toxin, is rendered negative by the injections of toxin. This loss of sensitivity of the skin has been thought to depend on the production of a specific scarlatinal antitoxin, such as occurs in patients convalescing from cases of clinical scarlet fever.
In a previous paper,2 it was suggested that the skin reaction