Not to penetrate too far into the realm of æsthetics, we will attempt to answer but two of its more obvious questions, which, however, are by no means simple ones. Whence is derived the strong emotional effect (1) of rhythm and (2) of melody? (Some thoughts on the acoustic effects of poetry will be presented in the next section.) Rhythm may be regarded as the most salient quality of music, and seems to have antedated melody considerably among primitive peoples. While nothing is easier than to recognise the pleasure it affords, the derivation of its exciting effect on the emotions is most difficult to trace. Widely diverse theories have been advanced in the various attempts to solve this riddle. Rhythm is a conspicuous instance of the unity in variety which characterizes beauty. It satisfies this intellect, and is calculated to rivet the attention by exciting expectation. It answers to our own organization; the step, the heart-beat, breathing, the natural physical processes, are all rhythmic, as well as the alternation of waste and repair in the nervous system. But while these facts undoubtedly contribute to our enjoyment of rhythm, they can hardly account adequately for its intense emotional effects. At this point the Darwinist comes to the rescue, and says that its employment in courtship sufficiently explains these effects, taking into account their hereditary association. He dwells on the sexual excitation which quivers in the purest enjoyment of music, and is “likely to excite in us in a vague and indefinite manner the strong emotions of a long-past age.”[48] Far be it from me to discard this hypothesis hastily, particularly as I have no better one to offer, but since it appears to afford but a meagre chance of solving the problem, we may venture to seek enlightenment in another supposition. It is to be found in Souriau’s system of æsthetics, which in my opinion is not yet fully appreciated. As Nietzsche has said, “As in art, so with any æsthetic fact or appearance, a physiological condition of transport is essential,”[49] so, too, Souriau insists that art employs every possible means to induce in us a semi-trance or hypnotic state, and through it renders us approachable to a degree which would be impossible when we are normally alert.[50] Now, rhythm is to the last degree such a transporting agency, owing to its strong hold on the attention. Weinhold and Heidenhain have induced hypnosis by means of the ticking of a watch, and in so doing have only employed an agency which has similar uses the world over. Just as most of the inhabitants of the earth have learned the use of narcotics, so too are they eager to adapt such an intoxicant as rhythm proves to be.[51]