STUDIES ON TREPONEMA PALLIDUM AND SYPHILIS : III. THE INDIVIDUAL FLUCTUATIONS IN VIRULENCE AND COMPARATIVE VIRULENCE OF TREPONEMA PALLIDUM STRAINS PASSED THROUGH RABBITS.

1. As regards these strains, at least, there is no consistent change, either increase or decrease, of rabbit pathogenicity during progressive rabbit passage. 2. There is no difference in pathogenicity between these different strains, although some of them were isolated from condylomata, some from chancres, one from a mucous patch, and one by Nichols from the nervous system. 3. We do not believe that there is any consistency of difference in speed of incubation between these various strains. 4. We think that the nature of the lesion produced by any individual strain, and the incubation time as well, are dependent upon the fortuitous factors incident to the nature of the material used, the technique of injection, and the size of rabbit in which the injection is made. As to the tendency to generalize possessed by one strain or another, we are not prepared to make a statement. We have not inspected as carefully as we might all our rabbits in regard to the more obscure syphilitic lesions such as small nodules on the eyebrows, nodules on the nasal bones, and internal lesions of the eye. As a matter of fact, we have noticed three cases of keratitis, probably syphilitic, and a number of preputial metastases, we have seen occasional nodules about the anus, and in one case a peritonitis in the fluid of which living treponemata were found on examination. There has not been in our series an extensive number of generalizations. We attribute this largely to the fact that all the studies here recorded were made on rabbits intratesticularly inoculated. It appears from the writings of other investigators that intravenous and intracardial injection of rabbits leads to a more extensive metastatic or general distribution. Two of the few rabbits inoculated intravenously showed testicular lesions. A series of rabbits intracerebrally inoculated through trephine openings showed nothing definite on autopsy, though one of them showed interference with reflexes and rigidity of the limbs for a time which seemed significant of pathological change. This rabbit, however, recovered entirely.