A few words in explanation are needed. In my summer course of lectures on Medical Psychology and Mental Diseases delivered in the University, I have to investigate the human mind in its practical relations to the body, and especially I have to teach how each influences the other, so that the physician, or any intelligent person, may be able to modify these relations beneficially. The starting-point in these inquiries is the fundamental fact of experience, that no changes in the mind or the consciousness of whatever kind can or do arise, or continue, without a corresponding series of changes somewhere in the brain-tissue.