I believe we are in harmony with the teachings of general pathology in assuming that this development involves two dangers, inhibition and regression. In other words, with the universal tendency of biological processes toward variation, it must necessarily happen that not all preparatory phases of a given function are equally well passed through or accomplished with comparable thoroughness. Certain components of a function may be permanently held back in an early stage of development and the complete development is therefore retarded to a certain extent. Let us seek analogies for these processes from other fields. If a whole people leaves its dwellings to seek a new home, as frequently happened in the early periods of the history of mankind, their entire number will certainly not reach the new destination. Setting aside other losses, small groups or associations of these wandering peoples would stop on the way, and, while the majority passes on, they would settle down at these way-stations. Or, to seek a more appropriate comparison: You know that in the most highly evolved mammals, the male seminal glands, which originally are located in the far depths of the abdominal cavity, begin to wander during a certain period of intra-uterine life until they reach a position almost immediately under the skin of the pelvic extremity. In the case of a number of male individuals, one of the paired glands may as a result of this wandering remain in the pelvic cavity, or may be permanently located in the canal through which both glands must pass in their journey, or finally the canal itself may stay open permanently instead of growing together with the seminal glands after the change of position has taken place normally. When, as a young student, I was doing my first piece of scientific research under the direction of von Brücke, I was working on the dorsal nerve-roots in the spinal cord of a small fish very archaic in form. I discovered that the nerve ganglia of these roots grow out from large cells which lie in the grey matter of the dorsal column, a condition no longer true of other vertebrates. But I soon discovered that such nerve cells are found outside the grey matter all the way to the so-called spinal ganglion of the dorsal root. From this I concluded that the cells of this group of ganglia had traveled from the spinal cord to the roots of the nerves. This same result is attested by embryology. In this little fish, however, the entire path of the journey was traceable by the cells that had remained behind. Closer observation will easily reveal to you the weak points of these comparisons. Therefore let me simply say that with reference to every single sexual impulse, I consider it possible for several of its components to be held back in the earlier stages of development while other components have worked themselves out to completion. You will realize that we think of every such impulse as a current continuously