This preternaturally large output of laughter during a prolonged state of high spirits finds its explanation in part in a kind of physiological inertia, the tendency to go on repeating movements when once these are started. The protracted iteration of laughter in a child is closely analogous to that of his half-unconscious singing to himself. This tendency of movements to perpetuate themselves in a mechanical way probably accounts for the lengthening of the single outburst in the case of a child violently seized with mirth. As mothers know, this reduction of laughter to a mechanical iteration of movement is apt to continue beyond the limits of fatigue and to bring on such unpleasant effects as “hiccup”. It is probable, too, that the tendency during a prolonged state of mirth to recommence laughing after a short pause is referrible to a like cause: the physiological springs of the movements being once set going, the explosive fit tends to renew itself. Discounting this effect of physiological inertia, we seem to find that in these periods of prolonged high spirits laughter retains its fundamental character as a comparatively short process which occurs intermittently. Where the laughing is not merely a trick played off by the bodily mechanism, but holds a germ of mind in the shape of a happy consciousness, it has its large and significant pauses. If this is so, it seems reasonable to suppose that the mental antecedent which brings on some new explosion is analogous to the sense of “sudden glory” which accounts for the single joyous peal. Owing to the exceptionally strong disposition to laugh during such a period, the antecedent feeling need not be a powerful one, a very slight {75} momentary increase of the joyous tone sufficing to give a fresh start to the muscles. It is not difficult to suggest possible sources of such slight sudden augmentations of the happy feeling-tone. No prolonged state of consciousness is, strictly speaking, of one uniform colour; in the boisterous merriment of an old-fashioned dinner-party there were alternations of tone, brilliant moments following others of comparative dulness. The course of the bodily sensations in these prolonged states of joy is in itself a series of changes, involving a sequence of exaltations upon relative depressions of the “vital sense”. The course of the presentations to eye and to ear in such a festive mood must be subject to like fluctuations in respect of their action upon the feeling-tone; and the same applies to the flow of ideas which can find a place in the mind when thus affected. Lastly, it must not be forgotten that the movements of attention would of themselves always secure a certain rise and fall of enjoyment. We all know how, when we are gladdened by some new and unexpected happiness, the mind after a short digression returns to the delightful theme, and how, as a result of this return, a new wave of joyous feeling seems to inundate the spirit.