If, in the light of the previous discussion, we examine such facts as those here collected, we may easily trace throughout the perpetual operations of the same instinct.  It is everywhere the instinctive object of the male, who is very rarely passive in the process of courtship, to assure by his activity in display, his energy or skill or beauty, both his own passion and the passion of the female.  Throughout nature sexual conjugation only takes place after much expenditure of energy.[34] We are deceived by what we see among highly fed domesticated animals, and among the lazy classes of human society, whose sexual instincts are at once both unnaturally stimulated and unnaturally repressed, when we imagine that the instinct of detumescence is normally ever craving to be satisfied, and that throughout nature it can always be set off at a touch whenever the stimulus is applied.  So far from the instinct of tumescence naturally needing to be crushed, it needs, on the contrary, in either sex to be submitted to the most elaborate and prolonged processes in order to bring about those conditions which detumescence relieves.  A state of tumescence is not normally constant, and tumescence must be obtained before detumescence is possible.[35] The whole object of courtship, of the mutual approximation and caresses of two persons of the opposite sex, is to create the state of sexual tumescence.

It will be seen that the most usual method of attaining tumescence—­a method found among the most various kinds of animals, from insects and birds to man—­is some form of the dance.  Among the Negritos of the Philippines dancing is described by A.B.  Meyer as “jumping in a circle around a girl and stamping with the feet”; as we have seen, such a dance is, essentially, a form of courtship that is widespread among animals.  “The true cake-walk,” again, Stanley Hall remarks, “as seen in the South is perhaps the purest expression of this impulse to courtship antics seen in man."[36] Muscular movement of which the dance is the highest and most complex expression, is undoubtedly a method of auto-intoxication of the very greatest potency.  All energetic movement, indeed, tends to produce active congestion.  In its influence on the brain violent exercise may thus result in a state of intoxication even resembling insanity.  As Lagrange remarks, the visible effects of exercise—­heightened color, bright eyes, resolute air and walk—­are those of slight intoxication, and a girl who has waltzed for a quarter of an hour is in the same condition as if she had drunk champagne.[37] Groos regards the dance as, above all, an intoxicating play of movement, possessing, like other methods of intoxication,—­and even apart from its relationship to combat and love,—­the charm of being able to draw us out of our everyday life and lead us into a self-created dream-world.[38] That the dance is not only a narcotic, but also a powerful stimulant, we may clearly realize from the experiments which show that this effect is produced