A study of the subcultures of the Rawlins strain of Bacterium typhosum used by twelve different laboratories for vaccine production showed that they all differed from recently isolated smooth strains in cultural characteristics, virulence and protective efficiency.

Eleven of these Rawlins cultures gave both the flagellar and the somatic type of agglutination in anti-smooth rabbit serum, and the one culture so tested produced both flagellar and somatic agglutinins when injected into rabbits and man.

Agglutination of neither the flagellar nor the somatic type can, therefore, be used as a test of the smoothness of a culture or as an index of immunity.

Since the Rawlins strain differs from the smooth phase of Bacterium typhosumin cultural characteristics and in virulence, and is much less efficient than smooth strains as a protective antigen; and since the selection and maintenance of smooth cultures suitable for vaccine production present no serious difficulty, it would seem but logical to substitute virulent, smooth cultures for the very old Rawlins strain, if we are to expect the maximum protection from antityphoid vaccination.

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