While I regard Moll's analysis as a valuable contribution to the elucidation of the sexual impulse, I must repeat that I cannot regard it as final or completely adequate. As I understand the process, contrectation is an incident in the development of tumescence, an extremely important incident indeed, but not an absolutely fundamental and primitive part of it. It is equally an incident, highly important though not primitive and fundamental, of detumescence. Contrectation, from first to last; furnishes the best conditions for the exercise of the sexual process, but it is not an absolutely essential part of the process and in the early stages of zoölogical development it had no existence at all. Tumescence and detumescence are alike fundamental, primitive, and essential; in resting the sexual impulse on these necessarily connected processes we are basing ourselves on the solid bedrock of nature. Moreover, of the two processes, tumescence, which in time comes first, is by far the most important, and nearly the whole of sexual psychology is rooted in it. To assert, with Moll, that the sexual process may be analyzed into contrectation and detumescence alone is to omit the most essential part of the process. It is much the same as to analyze the mechanism of a gun into probable contact with the hand, and a more or less independent discharge, omitting all reference to the loading of the gun. The essential elements are the loading and the discharging. Contrectation is a part of loading, though not a necessary part, since the loading may be effected mechanically. But to understand the process of firing a gun and to comprehend the mechanism of the discharge, we must insist on the act of loading and not merely on the contact of the hand. So it is in analyzing the sexual impulse. Contrectation is indeed highly important, but it is important only in so far as it aids tumescence, and so may be subordinated to tumescence, exactly as it may also be subordinated to detumescence. It is tumescence which is the really essential part of the process, and we cannot afford, with Moll, to ignore it altogether.