THE PARASITOLOGY OF SYPHILIS

Syphilis has long been considered an infectious disease, but until recent years the discovery of the causal agent has eluded the most careful investigation. There has hardly been a pathologist or syphilographer of note who has not attempted to unravel the mystery. It would be impossible here to enumerate all the alleged causes that have been reported. Lassar has said that during the past twenty-five years at least 125 causes have been assigned to syphilis. It is evident that the great majority of these theories were very short-lived. There are three, however, that deserve mention. The bacillus which Lustgarten described in 1885 occupied the stage for several years, being defended by so good an observer as Weigert, but later it was shown to be identical with the smegma bacillus. The next appearance was Neissen's so-called syphilis bacillus. Recently Neissen¹ has published the results of his fifteen years'