In 1904 Ehrlich summarized the aims of chemotherapy: "What we seek is `specific chemotherapy,' that is, we are in the search of a drug which should be capable of destroying certain parasites without at the same time causing too much damage to the host." Since that time chemotherapy has accomplished notable successes in the treatment of diseases caused by protozoa and spirochetes and more recently by other bacteria. The use of organic arsenical compounds in the treatment of syphilis, of plasmochin and atabrine in malaria, of quinoline derivatives in ameba amebiasis and of antimony compounds in the treatment of leishmaniasis is well established. In the case of bacterial disease the problem proved to be much more difficult because the organisms are much less differentiated. Koch's failure to cure guinea pigs infected with anthrax by injection of mercuric salts discouraged, at least temporarily, much research in this field.
The preparation by