The
intravenous injection into rabbits of
suspensions of dead T. pallidum derived from rabbit testicular chancres regularly caused the appearance of Wassermann and flocculation
antibodies in significantly increased titer. Control
suspensions of cultured treponemes (Reiter strain) added to extracts of normal testes were ineffective. This suggests that the Wassermann and flocculation
reagin elaborated during syphilitic
infection may be an antibody to T. pallidum which happens to cross-react with alcoholic extracts of mammalian tissue. The
antisera did not cause the agglutination of
suspensions of pathogenic T. pallidum, living or dead, did not give specific
complement fixation with those
suspensions, and did not usually cause the living treponemata to lose their infectiousness. Animals immunized with such aqueous
suspensions for as long as 4 months, or with organisms suspended in a water-in-oil
emulsion, were not demonstrably resistant to
infection. As few as ten living organisms inoculated intradermally into animals "immunized" with as many as 38 billion dead treponemata regularly produced typical darkfield positive
infections; and two of five animals inoculated intratesticularly with ten organisms were also infected. The contradiction involved in the production of
antibodies cross-reacting with a non-specific
antigen, and the non-appearance of specific
antibodies against the organism used as
antigen, is discussed in the text.