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