Of the two elements that compose the moral condition of mankind, our generalised knowledge is almost restricted to one. We know much of the ways in which political, social, or intellectual causes act upon character, but scarcely anything of the laws that govern innate disposition, of the reasons and extent of the natural moral diversities of individuals or races. I think, however, that most persons who reflect upon the subject will conclude that the progress of medicine, revealing the physical causes of different moral predispositions, is likely to place a very large measure of knowledge on this point within our reach. Of all the great branches of human knowledge, medicine is that in which the accomplished results are most obviously imperfect and provisional, in which the field of unrealised possibilities is most extensive, and from which, if the human mind were directed to it, as it has been during the past century to locomotive and other industrial inventions, the most splendid results might be expected. Our almost absolute ignorance of the causes of some of the most fatal diseases, and the empirical nature of nearly all our best medical treatment, have been often recognised. The medicine of inhalation is still in its infancy, and yet it is by inhalation that Nature produces most of her diseases, and effects most of her cures. The medical power of electricity, which of all known agencies bears most resemblance to life, is almost unexplored. The discovery of anæsthetics has in our own day opened out a field of inestimable importance, and the proved possibility, under certain physical conditions, of governing by external suggestions the whole current of the feelings and emotions, may possibly contribute yet further to the alleviation of suffering, and perhaps to that euthanasia which Bacon proposed to physicians as an end of their art. But in the eyes both of the philanthropist and of the philosopher, the greatest of all results to be expected in this, or perhaps any other field, are, I conceive, to be looked for in the study of the relations between our physical and our moral natures. He who raises moral pathology to a science, expanding, systematising, and applying many fragmentary observations that have been already made, will probably take a place among the master intellects of mankind. The fastings and bleedings of the mediæval monk, the medicines for allaying or stimulating the sensual passions, the treatment of nervous diseases, the moral influences of insanity and of castration, the researches of phrenology, the moral changes that accompany the successive stages of physical developments, the instances of diseases which have altered, sometimes permanently, the whole complexion of the character, and have acted through the character upon all the intellectual judgments,(147) are examples of the kind of facts with which such a science would deal. Mind and body are so closely connected that even those who most earnestly