How far these benign effects on health, which are recognised by the modern physician as well as by his predecessor, are due to the vigorous reinforcement brought by laughter to the work of respiration and of the circulation of the blood, it is not easy to say. The latter process reminds one of the circulation of pedestrians and vehicles in our London streets. In a general way it manages itself fairly well. Yet now and again a lusty “Move on!” from a policeman seems to be distinctly beneficial. Similar benefits may be extended to the organs of digestion and the rest. At the same time we must not lose sight of the possibility that laughter may act beneficially on our hard-pressed {36} frames in another way. As has been suggested above, the lusty cachinnation is nature’s way of voicing gladness, a sudden increase of pleasure. Now it has been held by psychologists that pleasurable feelings tend to further the whole group of organic functions, by adding to the nervous vigour which keeps them going. Laughter may owe a part of its benign influence on our bodily state to the fact that it produces a considerable increase of vital activity by way of heightened nervous stimulation.[21] One feature of the laughing outburst may pretty safely be ascribed to this increase of nervous action under pleasurable excitement. In all genuinely hilarious moods, the laugh is accompanied by a good deal of diffused activity of the voluntary muscles. This is seen most clearly in the unsophisticated laughter of children and savages. The sudden glee which starts the laugh starts also movements of arm, leg and trunk, so that arms flap wing-like, or meet in the joyous clap, and the whole body jumps. In older people matters may not be carried so far, though there are examples of the large shakings of laughter, notably that of Carlyle’s Teufelsdröckh, whose great laugh was one “not of the face and diaphragm only, but of the whole man from head to heel”; and it is hard perhaps for any man taken by the “stab” of a good joke to keep his arms down and his body vertical. It may be added that this supplementing of the energetic {37} respiratory actions by movements of the limbs gives to laughter its clear title to be called a muscular exercise. As such it is vigorous, voluminous and bordering, so to speak, on the violent. Its salutary influence, like that of the surgeon’s knife, will consequently depend on the celerity of its operation. Here we come to the other column in the reckoning. If laughter does good by its occasional irruption into a domain which otherwise would have too much of drowsy monotony, its benefit is rigorously circumscribed. Only too easily can it overdo the “flushing” part, and inundate and destroy when it should merely cleanse. In other words, the mirthful cachinnation, just because it is an irruption, a disorderly proceeding, must not be unduly prolonged.