Albert Neisser, the noted dermatologist from Breslau, went on study tours to Java in 1905 and 1907 in order to conduct experiments on monkeys to investigate a number of open questions concerning etiology, course and therapy of syphilis. These large-scale research efforts brought many results, which were somewhat overshadowed by more up-to-date investigations of other groups. Neisser considered his main achievement to be new insights into the immunity and therapy of syphilis.