THE IMMUNOLOGICAL SPECIFICITY OF STAPHYLOCOCCI : I. THE OCCURRENCE OF SEROLOGICAL TYPES.

1. Agglutination is not a precise method for the demonstration of serological types among staphylococci. 2. Precipitation of soluble specific substance derived from these organisms demonstrates the existence of at least two immunologically distinct types. 3. The one type, designated A, is composed of apparently virulent strains, while the other, Type B, contains the avirulent strains. 4. Precipitation tests performed with centrifugates of young broth cultures or with acid extracts of sedimented bacteria may also demonstrate type specificity. 5. Lysis by bacteriophage fails to detect the specific types of Staphylococcus. 6. Immunization by intravenous methods stimulates agglutinin formation in all rabbits and precipitin formation in only one of three or four animals. 7. Immunization by repeated intracutaneous injections of dead staphylococci or living organisms in an agar focus also stimulates agglutinin formation but fails to incite the formation of type specific precipitins.