In two previous papers,1 evidence has been presented to show that the skin of new-born infants is not sensitive to scarlatinal streptococcus filtrate toxin except in relatively few instances, and that the absence of this skin sensitivity is not due entirely to the presence of antitoxin. It was shown also that the skin of almost all infants more than 6 months of age has become sensitive to the toxin, although in some the sensitivity is more marked than in others. In a relatively small number, the skin does not show any reaction to considerable amounts of toxin. Some of these nonreactors have antitoxin in the blood, which presumably affects the sensitivity of the skin, while in the others antitoxin is not demonstrable. It was suggested2 that the skin sensitivity might be evidence of a specific hypersusceptibility of the body cells to protein substances formed by the scarlatinal streptococcus.