ABSTRACT
Manic-depressive psychoses form the second large group of mental disorders without discernible organic etiology. Quite early in the history of psychoanalysis, several contributions were made to the subject of these disturbances, but they were given systematic attention at a later date than the schizophrenias. The studies made have yielded much fundamental information with regard to the earliest evolutionary stages of the ego and libido; but as regards the theory of the disorder itself our knowledge is still incomplete, and many problems still await solution. At the beginning of the chapter on the schizophrenias it was stated that our exposition would necessarily be limited to the most essential issues. This same statement must be repeated here even more emphatically.
