The point may be significant, that the dominant antibody- evoking components of the variant could be determined best against the homologous strain and against strains isolated subsequent to the time of isolation of the strain which was parent to the variant; it seems, therefore, that analyses of antigenic structure which depend upon tests with only strains of virus which were isolated previous to time of isolation of the variant may furnish only partial information, and therefore, may be unreliable.
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