“…We have not found an early report of the use of the owl monkey-Aotus trivirgatus-a small nocturnal primate native to South America. In a previously published cooperative study of ocular syphilis and neurosyphilis (Smith, Singer, Reynolds, Moore, Yobs, and Clark, 1965), this monkey was used as the animal model because of its phylogenetic proximity to man, its large eyes in relation to a diminutive body size, and its availability. Findings in that study, as well as the phylogenetic position of the A. trivirgatus, interested us in further investigation of experimental syphilis in the species.…”