In our effort to follow up the origins of the sexual impulse, we have thus far found that the sexual excitement originates (_a_) as an imitation of a gratification which has been experienced in conjunction with other organic processes; (_b_) through the appropriate peripheral stimulation of erogenous zones; (_c_) and as an expression of some "impulse," like the looking and cruelty impulses, the origin of which we do not yet fully understand. The psychoanalytic investigation of later life which leads back to childhood and the contemporary observation of the child itself coöperate to reveal to us still other regularly-flowing sources of the sexual excitement. The observation of childhood has the disadvantage of treating easily misunderstood material, while psychoanalysis is made difficult by the fact that it can reach its objects and conclusions only by great detours; still the united efforts of both methods achieve a sufficient degree of positive understanding. In investigating the erogenous zones we have already found that these skin regions merely show the special exaggeration of a form of sensitiveness which is to a certain degree found over the whole surface of the skin. It will therefore not surprise us to learn that certain forms of general sensitiveness in the skin can be ascribed to very distinct erogenous action. Among these we will above all mention the temperature sensitiveness; this will perhaps prepare us for the understanding of the therapeutic effects of warm baths.