THE USUAL case of scarlet fever presents little difficulty in diagnosis by clinical means. However, there remains an appreciable number of cases in which the picture is not typical and in which diagnostic aids are desired. It is these questionable conditions that frequently go unrecognized and patients with them spread the disease to many other susceptible persons.
The reversal of the Dick reaction from positive to negative in a series of tests performed during the course of the disease is frequently employed to confirm the diagnosis of scarlet fever. If valid, this procedure should be of particular importance to the clinician and epidemiologist. The value of the Dick test for measurement of susceptibility to scarlet fever is universally recognized; however, much doubt still remains with respect to the worth of this test in the diagnosis of scarlet fever.
The present investigation is a study of the reactions to the Dick