These variations appear, so far as I can judge, to go with alterations of pitch. The broader sounds, e.g., aw, seem naturally to ally themselves to the hardier deep-pitched explosion, the others to the more cackle-like utterances in the higher parts of the register. This connection shows itself, too, in the change in the vowel-quality when, as frequently happens, the laugh runs through a cadence of pitch from a higher to a lower note.
These considerations will prepare us to find that the vowel-quality of the sound varies in general with sex and with age. According to Haller and Gratiolet the sounds of {32} the laughter of women and children, which correspond with their higher vocal pitch, approach in vowel-quality to the French i and e.[16]
Considerable variations from these typical forms would seem to occur now and again. In the American returns already referred to, the mode of laughing described is represented by such odd symbols as “gah! gah!” “iff! iff!” “tse! tse!” etc. These singularities, if, as it seems, they are intended to represent habitual modes of voicing mirth, are, one suspects, hardly referrible to natural differences of vocalisation, but are probably the result of the interfering agencies of nervousness and affectation which, as we know, have much to do with fixing the form of mirthful expression.
The description of laughter here offered applies only to the typical form. It would have to be modified considerably to suit the attenuated forms to which the expression is reduced in “polite society”. Of these, more presently. Even where the vocal outburst retains its primitive spontaneity and fulness considerable variations are observable, connected with differences in the whole respiratory and vocal apparatus. The intensity and volume of the sound, the pitch and vowel-quality, the rapidity of the successive expirations, the length of the series, the mode of commencing and of ending, may all exhibit variations which help to make the laughter of one person or of one race different from that of another.
We may now pass to some other accompaniments of the muscular movements of laughter. It is of importance to study these with care if we wish to estimate the precise value of the hilarious explosion in the economy of human life. {33}
Since the movements of laughter are sudden and violent interruptions of the smooth rhythmic flow of the respiratory process, we may expect to find that they have important organic effects, involving not merely the mechanism of respiration, but also that of the circulation of the blood. Here, it seems, we have to do with a double effect First of all (we are told), this series of spasmodic expirations—during which, as we have seen, the glottis is partially closed—increases the pressure within the thorax or chest, and so impedes the entry of blood from the veins into the heart. This effect is seen in the turgidity of the head and neck which appears after prolonged and violent laughing. In the second place, the exceptionally deep inspirations tend to expand the lungs with air, and to drain off the blood from the veins into the heart. The manner in which these two actions, the deepened inspiration and the prolonged expiration, alternate during a fit of laughter, appears to secure a considerable advantage in respect both of accelerated circulation and more complete oxygenation of the blood. The brisker movement of the blood after laughter has recently been observed in some experimental inquiries into the effects of emotional excitement of various kinds on the pulse.[17]
It is not improbable that this expedited circulation produces more remote effects on the organism. It has been suggested that one of the advantages of a “good laugh” is that it relieves the brain, and this would seem to imply that it quickens the movement of the blood through the fine and readily clogged vessels which permeate the brain-structures. {34}
And here we find ourselves face to face with the question: What truth is there in the saying that laughter has beneficial physiological effects? A curious chapter might be written on the views propounded, both by the light-hearted reveller and the grave and philosophic onlooker, on the wholesomeness of this form of “bodily exercise”. Only a bare reference to this aspect of the subject can, however, be given here.
To begin with, the unlearned, who know nothing of diaphragms or of congested veins needing to be relieved, have had a shrewd conviction that laughter sets the current of life moving briskly. Proverbs, such as “laugh and grow fat,” attest this common conviction. Those who have catered to the laughter-lovers have not unnaturally made much of this salutary influence. The mediæval writers of the laughable story in verse (the “fabliau” or “Conte à rire en vers”) held firmly to the belief in the “sanitary virtue” (“vertu saine”) of a burst of laughter.
This popular view has been supported by the weight of learned authority. Vocal exercises, of which laughing is clearly one, have been recommended by experts from the time of Aristotle as a means of strengthening the lungs and of furthering the health of the organism as a whole. By many, moreover, laughter has been specifically inculcated as a hygienic measure. The learned Burton (b. 1577) quotes a number of physicians in favour of the ancient custom of enlivening the feast with mirth and jokes.[18] The reader may find references to the salutary effects of laughter in the latest text-books of physiology. Both by a vigorous reinforcement of the actions of the large muscles which do the work of respiration, and, still more, by the beneficial effects of these reinforced actions on the functions of the {35} lungs and the circulatory apparatus, laughter properly finds a place among “bodily exercises”.[19]