Most drugs, toxins, hormones, and the like bring about their biologic actions by reacting with specific receptors somewhere in the body. Scientists working in all areas of biologic science have shown increasing interest in the analysis of drug-receptor interactions in the broadest sense. Studies of drugs (binding) to receptors in situ and to isolated and partly purified receptors are becoming common practice. The action of a drug in the body is, however, a kinetic event not only with respect to transport of drug molecules to the environment of the receptors, but also with respect to the...