Probably the greatest advancement in the field of pharmaceutical therapeutics was brought about by the result of Ehrlich's famous 606th experiment, with its modifications. The treatment of syphilis and yaws became quickly revolutionized and that of relapsing fever became established. Other therapeutic procedures by this agent are being molded slowly for equally common and almost equally serious diseases, but with cures of a less spectacular nature. Moreover, the value of this arsenical agent in these latter conditions is not so striking because these diseases have other specifics which, however, also have their limitations.
Tropical medicine affords an exceptionally wide field for extra-syphilitic uses of dioxydiamidoarsenobenzol and its modifications and I feel that the full value of this drug in some of the tropical and subtropical diseases is not, as a whole, sufficiently appreciated. I need only mention yaws, gangosa and relapsing fever.