The treatment of syphilis with mercury over the years proved wholly unsatisfactory because such "cures" as it produced were principally symptomatic and rarely, if ever, biologic. With the introduction of the trivalent organic arsenicals the situation changed radically and the much-hoped-for goal of a true biologic cure became a reality. In the experimental animal it was demonstrated that a few doses of the organic arsenicals could completely destroy the treponemes and thus bring about a biologic cure. It was further found that in man even a single adequate dose of the arsenical was capable of curing yaws, a disease closely related to syphilis. Unfortunately, this desideratum was unattainable in human syphilis since large doses, frequently repeated, were necessary. This often resulted in serious toxic reactions and in relapse. This situation soon led to the abandonment of such intensive methods of treatment.
In consequence many prolonged schemes of