The recognition of this identity of the two actions is evidenced by the usages of speech. We see in the classical languages a tendency to employ the same word for the two, laughing like smiling being regarded—primarily and mainly at least—as an object of visual perception. This is particularly dear in the case of the Latin “ridere,” which means to smile as well as to laugh, the form “subridere” being rare. This tendency to assimilate the laugh and the smile as facial expressions was naturally supplemented by the employment, both in Greek and in Latin, of a separate word for audible laughter (“καχάζειν”, “cachinnare”) in cases where it was needful to emphasise the fact of sound. In some modern languages the relation of smiling to laughing is precisely indicated as that of a less full to a fuller action (Italian, “ridere” and “sorridere”; French, “rire” and “sourire”; German, “lachen” and “lächeln”). Possibly the existence of two unrelated words in our own and some other modern languages points to the fact that certain races have been more impressed by the dissimilarity between the audible and the inaudible expression than by the similarity of the visible manifestations. {30} It is worth noting that even after the two expressions have been distinguished by separate names there is a tendency to use the stronger metaphor “to laugh,” rather than the weaker one “to smile,” in describing the brighter aspects of nature’s beauty, such as meadows when in flower. A painter, whom Dante meets in Purgatory, and recognises as the first in the art of illumination, gracefully transfers this distinction to a brother painter by saying that the leaves which the latter painted “laugh more” (piu ridon) than his own.[15] We may now turn to the distinguishing characteristics of laughing, that is, the production of the familiar series of sounds. Like sighing, sobbing and some other actions, it is an interruption of the natural rhythm of the respiratory process, in which inspiration and expiration follow one another at regular intervals. The obvious feature of this interruption in the case of laughter is the series of short, spasmodic, expiratory movements by which the sounds are produced. These are, however, preceded by a less noticed inspiration of exceptional energy and depth. These interruptions of the ordinary respiratory movements involve an unusually energetic action of the large muscles by which the chest is expanded, _viz._, those which secure the contraction and so the descent of the dome-shaped diaphragm, and those by the action of which the ribs are elevated.