The author defines its purpose on p. 65 of this book as follows: 'To incorporate into the theory of sexuality certain discoveries made in patients suffering from manic-depressive states'. In our opinion he has not only brilliantly fulfilled the task that he set himself, but he has done far more than this. In the first place his book throws fresh light on the normal and pathological conditions in psycho-sexual development, for he demonstrates facts hitherto unrealized and fits them into the framework of the libido-theory. Secondly, the new knowledge to which he introduces us illuminates the instinctual dynamics of certain clinical pictures, which analysis had so far been unable to explain. Finally, the book makes a contribution of the utmost importance to the psychology of these morbid states. Our understanding of melancholia and mania (in which Freud was the pioneer) is greatly enlarged by this book. The author shows in a convincing manner