Before the circulation of the blood was discovered, the pathology of diseases of the heart must have been unknown, and their treatment empirical and of little effect. Before the discovery of the glycogenic function of the liver, the pathology of diabetes remained a mystery, and its treatment a matter of guess-work. In all dealings with the facts of life, the science of the normal must precede the science of the abnormal. In the domain of mental operations the science of the normal is of very modern discovery, and Alienism, the science of the abnormal, has consequently been until recently compelled to limit itself to collections of materials for future use, and to tentative groupings of these materials which have necessarily been provisional on their harmonizing with the future developments of the science.