17.--Neuroglia cells from the spinal cord 122 18.--An artery from the cerebral cortex 125 19.--Neuroglia cells of the superficial layers of the brain from an infant aged two months 126 20.--Complexity of cell of the central nervous system 131 21.--Section through the cortex of the gyrus occipitalis superior 132 22.--Motor cell of ventral horn of spinal cord from the human fetus 133 23.--Normal diaphragm curve in normal breathing 577 24.--Curve in diaphragm before and during talking by a stutterer 577 25.--Illusion of dual vision 615 26.--Illusion of dual vision 767 27.--Binocular vision 767 28.--Binocular vision 767 29.--The Mueller-Lyer lines 768 30.--Illusions of size 769 31.--Illusion of filled space (interrupted vision) 769 32.--Illusions of size and linear continuity 770 33.--Poggendorf's displacement of oblique lines 771 34.--Zoellner's distortion of parallel lines 772 {1} PSYCHOTHERAPY INTRODUCTION To physicians who are students not alone of the manifestations of disease but also of the workings of human nature, there are few chapters in the history of medicine more interesting than those which record the welcome by each generation of the supposed advances in the treatment of disease. Each generation announced its cures for diseases, provided its remedies to relieve symptoms, and invented methods of treatment that seemed to put off the inevitable tendency toward dissolution. Yet few of these inventions and discoveries maintain their early reputations, and succeeding generations invariably abandon most of this supposed medical progress in favor of ideas of their own, which later suffer a like fate. Plausible theories have not been lacking to support the successive remedies and methods of treatment, but the general acceptance of them was always founded far less upon theory than upon actual observation of their supposed efficacy. Certain remedies were given and the patients began to improve. Patients who did not have the remedies continued to suffer, and sometimes the course of their disease led to a fatal termination. Even with the best remedies death sometimes took place, but that was easily accounted for on the ground that the disease had secured so firm a hold that it could not be dislodged, even by a good remedy. The connection of cause and effect between the administration of the remedy and the improvement and eventual cure of the patient seemed to be demonstrated.