Although it was claimed by Klebs as long ago as 1879 that syphilis could be artificially produced in apes, the subject did not receive much attention till a few years ago, when Metchnikoff and Roux took up the work afresh at the Pasteur Institute. The success of these investigators led to further research, in which a prominent part has been taken by Neisser of Breslau and Finger of Vienna.
The researches of Metchnikoff and Roux were carried out on the higher anthropoid apes, the chimpanzee especially being used. It was shown that syphilis could be inoculated into these animals with the production of a primary lesion, after a period of incubation, followed later by secondary manifestations. Metchnikoff and Roux laid stress on the fact that anthropoid apes were necessary, but later experiment has shown that some varieties whose relationship to man, as shown by the precipitin test, is remote, may