Until comparatively recently, the greater part of research work in helminthology progressed along three main lines, investigation into the life histories of parasitic helminths, the study of their morphology as well as an empirical investigation into the efficiency or otherwise of different substances as anthelmintics. Research into the physiology of these animals was only rarely attempted and even then was only very casual and never by any means thorough. In recent years, however, there has been a gradual change over, and increased attention has been paid to their physiology, both from a purely scientific and also an applied standpoint. Early work on anthelmintics was concerned only with the discovery of substances which would expel the worms from their hosts and could be used empirically. This attitude has of recent years, given place to a more scientific approach in which investigations into physiological processes have been undertaken in the hope that knowledge gained might show some method of rendering the worms more susceptible to anthelmintics, or alternatively, indicate new anthelmintics more lethal to them and less harmful to the hosts.