522 THE POPULAR SCIENCE MONTHLY. 



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 di- 

 rection, 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. Never- 

 theless, 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 appa- 

 ratus 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 upper- 

 most rings of the bronchi. Commonly the larynx is divided in its in- 

 ferior 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 cor- 

 responding 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 >rattling is not 

 impaii-ed 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 





