THE chemotherapeutic armamentarium of the physician has recently grown considerably. The question is no longer merely whether to give penicillin; the choice must now be made among half a dozen or more efficient antimicrobial agents that can be used to advantage in many infectious processes. With the availability of several good drugs the idea naturally arises of using them in combinations rather than singly. It appears reasonable to suppose that if one drug is useful two employed simultaneously should be better and three should ensure the patient's recovery. Considerations of this kind have led to a great increase in the . . .