1. Two principal types of gonococci may be recognized by suitable immunological tests; e. g., agglutination and complement fixation. These two types correspond to the adult and infant types of infection with the gonococcus, seen clinically.
2. On the basis of the immunological reactions of agglutination and complement fixation the strains of gonococci isolated from three cases of ophthalmia are classed with the adult type.
3. A polyvalent antigen for the serological diagnosis of a gonococcus infection should represent strains of the infant type of organism in order that both types of infection, infant as well as adult, may be recognized.