Experimental ocular and neurosyphilis in the primate.

The rabbit has been commonly used for experimental syphilis since Bertarelli (1906) first inoculated this species with Treponema pallidum. Three years earlier, Metchnikoff and Roux (1906) had succeeded in making the monkey the first animal successfully inoculated with the disease. However, but for isolated and notable exceptions (Neisser, 1906, 1908; Turner and Hollander, 1957), few subsequent studies of experimental syphilis have been performed in the primate. Because of interest in the clinical problem of sero-negative ocular and neurosyphilis (Smith, 1964, 1965; Smith, Singer, Moore, and Yobs, 1965; Smith and Taylor, 1965), here defined as late syphilis in which serum reagin tests are non-reactive but which can be detected by specific treponemal tests, a study of experimental syphilis in the primate was begun in this laboratory in 1963. During the past 3 years, the owl monkey (Aotus trivirgatus) and the squirrel monkey (Saimiri sciurea) have been found to be especially suitable species for ophthalmological investigation (Smith, Singer, Reynolds, Moore, Yobs, and Clark, 1965; Taylor, Smith, and Singer, 1965). These small primates are inexpensive, hardy in nature, and safe as a laboratory animal. They possess obvious advantages over the rabbit in having fundi quite similar to man, and in not having laterally placed eyes, an important point when studying pupillary function. The owl monkey has larger eyes and has hence been preferred for anterior segment technical reasons, but the fundus of the squirrel monkey is more like that of man (Smith, Reynolds, Rane, and