In the spring of 1911, the members of the meningitis department started to investigate the possible grouping of strains of the meningococcus, being led thereto by Torrey's (1) success in demonstrating the division of strains of gonococcus into groups. The desirability of some definite knowledge on this point is obvious. Not only is it of academic interest, but in the preparation of anti-meningitis serum, it is of the utmost importance that, if the strains differ in their serological reactions and may be classified thus, as many groups as possible should be represented. Also in view of the large number of strains that may be collected, it is a great saving of time and media, if the multiplication of similar strains may be avoided without lessening the therapeutic value of the serum.

Three methods at once suggested themselves—agglutination, opsonic tests, and complement fixation. The agglutination method proved unsatisfactory.

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