Abstract
THE use of the complement-fixation test in serologic investigation serves as a frequent reminder to the physician of the existence of the complement system. It is probable that despite the advances that have taken place in the last decade in knowledge of this complex system, many students still emerge from their medical studies with a somewhat antiquated concept of its nature and importance. For the sake of emphasis one might say that although the complement system may serve to defend the host against invasion by infectious organisms, it may also have an important role as a final common pathway of . . .