That is to say, the evidence from the abounding laughter of childhood—pre-eminently a period of rapid physical growth and of the accumulation of a large store of nervous energy—as also the evidence from the laughter of unusually mirthful adults, who are, as a rule, persons of large build and of corresponding nervous force, suggests irresistibly the conception of laughter as an instinct implanted in us for the performance of an important physiological function. This view finds additional support in the familiar “giggling silliness” of the adolescent period, that strange period of unusual growth and stress, and the one in which are most likely to occur those singular attacks of untimely hilarity at funerals and on other solemn occasions, as mentioned among the responses to President Hall’s questionnaire. No more than the little child or your friend the jolly man does the adolescent always know at what he is laughing. He simply knows that he is impelled to laugh by forces latent in his being and over which he has no control. Nor is it only as a relief from neural tension that laughter benefits the one who laughs. In the studies of laughter in childhood made by such investigators as Preyer, Sully, and Miss Shinn, one finds frequent allusion to occasions when laughter is obviously a reaction from a state of mental strain, and has a specifically useful effect in easing the mind. There is reason to believe that this is actually one of its constant ends—that it is a device for lightening the burden of mentation by temporary interruption of the thought process. As all educators are well aware, the first years of life and the adolescent period are not only the years of greatest physical growth, but the years when the severest demands are made on the mind, both by the task of acquiring knowledge and by the perturbations of adolescence. They are the years when the mind, in its immaturity, is most in need of some protective mechanism to enable it automatically and at frequent intervals to take a holiday as it were. Such a mechanism is admirably provided in laughter, which, as every laugher will at once appreciate, when not unduly prolonged leaves behind it a pleasurable feeling of exhilaration and greater mental as well as physical well-being.