In the course of rapid passages through mice a strain of group A type 27 hemolytic streptococcus was found to have lost its group carbohydrate without the loss of type-specific precipitinogens, agglutinogens, or its capacity to induce protective antibodies in rabbits, and without the acquisition of the carbohydrate of another group.

The loss of group carbohydrate was shown to be complete, within the limits of the methods for its detection. Extracts of the anomalous strain did not react with group A antisera; and antisera prepared with organisms of this anomalous strain did not contain demonstrable antibodies for the group carbohydrate. Bacterial suspension of the anomalous strain failed to absorb any appreciable amount of group-specific antibody.

The fact that the anomalous strain lacking group-specific carbohydrate, C, was derived from the original was established by the demonstration of persistence of its other characteristics, in particular the precipitinogens, agglutinogens, and antigens responsible for protective antibodies of type 27.

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