SINCE Bertarelli1 in 1907 discovered that rabbits could be successfully inoculated with Treponema pallidum the rabbit testicle has been the main source of the live virulent cultures used in experimental syphilis. Kolle and Schlossberger2 in 1926 found that the white mouse also could be successfully inoculated with syphilis (symptomless infection?) and after a number of days (the incubation period varying for the different organs—e.g., lymph nodes, thirty days; spleen, fifty days and brain, one hundred and fifty days) these mouse tissues would produce a specific orchitis in about sixty days after injection into rabbit testicle.
During the past eighteen years laboratory strains of S. T. pallidum have been perpetuated in this manner, either by rabbit to rabbit or by rabbit to mouse and mouse to rabbit transfers. The presence of the S. T. pallidum in the various mouse organs (brain excepted) has been demonstrated by