Page:Popular Science Monthly Volume 9.djvu/548

522 forest recesses of the New World, can be heard, says Humboldt, at the distance of a kilometre and a half, and farther still according to other travelers. In the elephant the lateral cartilages of the larynx do not come into mutual contact, and the vocal cords, having an oblique direction, seem to be incapable of great tension; hence the voice of the elephant is deep, but at the same time very powerful. If we could observe in animals the play of the larynx during the emission of the voice, we should discover many curious and instructive actions of the glottis. But here we meet with an almost insuperable difficulty, for we can place but little reliance on the good-will of animals. Nevertheless, Mandl, trusting to his skill in the use of the laryngoscope, by no means despairs of success, knowing well that by dint of patience we often succeed in removing the most formidable obstacles. After man, birds hold the most prominent place among animate things in the concert of Nature; they enliven field, forest, and garden, with an infinity of chirrupings, leading one's thoughts to dwell on the pleasure of living. The structure and mechanism of the vocal apparatus of birds have been studied by many naturalists. George Cuvier discovered the precise point where the voice is formed. Birds have two larynges, one at the top of the trachea, and the other at the bottom. It is the latter alone which produces the sounds: the former acts only as a resonator. This is easily shown by experiment: if we cut the trachea in the middle, the voice remains. The vocal organ has the form of a box, to which anatomists give the name of drum. It is formed of the lowermost rings of the trachea and the uppermost rings of the bronchi. Commonly the larynx is divided in its inferior portion, sometimes by the angle of union of the bronchial tubes, again by a bony plate which serves as a point of attachment for a membrane rising from the inner margin of each of these tubes, and bounding the glottis with an opposing prominence, the edge of which is elastic. Thus two lips discharge the functions of vocal cords; they become tense or relaxed by the action of a muscular apparatus which in some cases is very simple, in others highly complex. The enormous variety which obtains in the vocal powers of birds necessitates a corresponding diversity in the details of the structure of the larynx and in the conformation of the trachea.

Parrots, being social in their nature, live in large flocks in the most favored climates of the globe; their habit of prattling is not impaired by captivity. When several individuals are together, they appear sometimes to engage in interminable conversations. On the alert for every voice-sound, and even for every noise, parrots imitate these with wonderful ease; thus they readily imitate the articulate speech of man, a phenomenon as yet unexplained. The movements of the tongue, no doubt, play an important part in the articulation of these sounds, but the nature of the resonances leads us to suspect a special activity of the superior larynx. The researches which have