I now turn to a very much more serious and elaborate attempt to define the constitution of the sexual impulse, that of Moll.  He finds that it is made up of two separate components, each of which may be looked upon as an uncontrollable impulse.[19] One of these is that by which the tension of the sexual organs is spasmodically relieved; this he calls the impulse of detumescence,[20] and he regards it as primary, resembling the impulse to empty a full bladder.  The other impulse is the “instinct to approach, touch, and kiss another person, usually of the opposite sex”; this he terms the impulse of contrectation, and he includes under this head not only the tendency to general physical contact, but also the psychic inclination to become generally interested in a person of the opposite sex.  Each of these primary impulses Moll regards as forming a constituent of the sexual instinct in both men and women.  It seems to me undoubtedly true that these two impulses do correspond to the essential phenomena.  The awkward and unsatisfactory part of Moll’s analysis is the relation of the one to the other.  It is true that he traces both impulses back to the sexual glands, that of detumescence directly, that of contrectation indirectly; but evidently he does not regard them as intimately related to each other; he insists on the fact that they may exist apart from each other, that they do not appear synchronously in youth:  the contrectation impulse he regards as secondary; it is, he states, an indirect result of the sexual glands, “only to be understood by the developmental history of these glands and the object which they subserve”; that is to say, that it is connected with the rise of the sexual method of reproduction and the desirability of the mingling of the two sexes in procreation, while the impulse of detumescence arose before the sexual method of reproduction had appeared; thus the contrectation impulse was propagated by natural selection together with the sexual method of reproduction.  The impulse of contrectation is secondary, and Moll even regards it as a secondary sexual character.

While, therefore, this analysis seems to include all the phenomena and to be worthy of very careful study as a serious and elaborate attempt to present an adequate psychological definition of the sexual impulse, it scarcely seems to me that we can accept it in precisely the form in which Moll presents it.  I believe, however, that by analyzing the process a little more minutely we shall find that these two constituents of the sexual impulse are really much more intimately associated than at the first glance appears, and that we need by no means go back to the time when the sexual method of reproduction arose to explain the significance of the phenomena which Moll includes under the term contrectation.