The present researches form a series of cases the investigation of which is undertaken with the object of studying the problems presented by the phenomena of functional psychosis. Out of a mass of material we have selected a few cases typical of many others, each case standing for a type. As much as possible we have tried to avoid theories and principles and give simply a resume of the facts and experiments. The more general aspects of these cases and the conclusions flowing from similar observations and experiments are relegated to another work soon to appear under the title of Principles of Psychology and Psychopathology. The cases are more in the nature of laboratory researches, each case standing on its own individual merits; they are all, however, intimately interconnected, representing various phases and stages of the processes of mental dissociation.<br><br>The methods of work of this series, as well as of the series to come, have all of them been developed in the psychopathological laboratory, - the researches being carried on in the laboratory or at other places under its direction.