90 THE DICK TEST IN SCARLET FEVER PATIENTS AND IN NORMAL INDIVIDUALS

SINCE Dick and Dick (1924) published their method of testing the susceptibility or insusceptibility of human beings to scarlet fever various other workers have reported investigations which have confirmed the observations of the Dicks. Zingher (1924 a—d) found that 98 per cent, of cases of scarlet fever gave a positive reaction with the Dick test during the first five days of the disease, while during convalescence 19 per cent, of cases still showed a positive reaction. He believed that the Dick test was a reliable index of immunity and susceptibility to scarlet fever and was of opinion that, when a strongly positive Dick test was obtained in a patient ill for five or six days, the positive reaction should be regarded as evidence against the patient having had scarlet fever. Branch and Edwards (1924) tested sixty-five convalescent cases of scarlet fever and found that all gave negative Dick tests. Dick and Dick (1925) in a series of 204 patients who had previously had scarlet fever found that 9-3 per cent, reacted positively. Eosen and Korobicina (1925) reported that they had studied the Dick test in 123 cases of scarlet fever and found that 82-5 per cent, were positive on the second day of the disease, 74-1 per cent, on the fourth day, 50 per cent, on the fifth day and 17-2 per cent, during convalescence. Kerr (1925) and co-workers tested 441 cases of scarlet fever and obtained positive reactions in 73-7 per cent, of cases during the first three days of the disease and in 7-3 per cent, of cases during convalescence, while O'Kell and Parish (1925) in 120 convalescent cases obtained positive reactions in 18 per cent, of cases. Brown (1925) tested the reactions of scarlet fever cases with two dilutions of toxin, 1 in 6000 and 1 in 1000. With the 1 in 6000 toxin only 26-6 per cent, of thirty cases of acute scarlet fever gave a positive reaction, while with toxin diluted 1 in 1000 seven acute cases all gave positive reactions. In ninety patients with a history of having had scarlet fever or convalescing from scarlet fever 8-8 per cent, of cases gave a positive reaction with toxin diluted 1 in 6000, while in twenty-five convalescent cases tested with 1 in 1000 dilution positive reactions were obtained in 32 per cent, of cases.