is a veritable vivisection of the mind by the mind’s own vital forces, and as such gives us much more definite and precise data for the determination of normal mental mechanisms and processes than can introspective analysis; just as the vivisection of the body in the laboratory and by disease has given us our most precise knowledge of physiology. Consequently the phenomena acquire a greater interest and value from the insight they give into the normal. For there is no more fruitful material for the study of the mechanisms and processes of personality than cases of this sort where there is a disintegration of the normally integrated structural wholes and a reassembling of the component elements into new composite wholes. In the construction of these new personalities certain normal structures and mechanisms are dissected out, so to speak, of the original composite by the stress of the forces that cause the cleavage between systems and are then reassembled into new functioning wholes. There is a veritable vivisection of the mind. In a mind thus disassembled nearly every mental phenomenon, conscious and subconscious—conflicts, hallucinations, coconscious processes, defense reactions, etc.,—can be observed in an isolated form and systematically studied. They are veritable gold mines of psychological phenomena, as William James once expressed it to me in reference to one of my cases. It is strange, therefore, that such cases have been neglected by psychologists who would study mental mechanisms. It is true that for a complete understanding of multiple personality a study of a number of cases should be presented, particularly as many variations are to be observed constituting differing types. But in a volume of this kind this would be impracticable. I have, therefore, limited myself to the psychogenesis of a single case, that of B. C. A. This will I believe be of interest not only as illustrating the basic principles underlying the pathology of multiple personality, but because of the data it offers for the understanding of the structure and mechanisms of the normal self, something that curiously appeals to the egoistic interest of human nature. MORTON PRINCE. TABLE OF CONTENTS PAGE PREFACE TO FIRST EDITION v PREFACE TO SECOND EDITION xiii LECTURE I. THEORY OF MEMORY AS A PROCESS 1 II. CONSERVATION OF FORGOTTEN EXPERIENCES OF NORMAL, 15 ARTIFICIAL, AND PATHOLOGICAL LIFE III. CONSERVATION OF FORGOTTEN EXPERIENCES OF NORMAL, 49 ARTIFICIAL, AND PATHOLOGICAL LIFE—(Continued) IV. CONSERVATION A RESIDUUM OF EXPERIENCES 87 V. NEUROGRAMS 109