HUMBOLDT ON THE OKGANS OF THE VOICE. 



343 



the arytenoid cartilages bent forward, in order to display the internal 

 structure of the glottis. I did not find sacs in the inferior larynx 

 of this bird, but simply a bulging out and broadening of the last 

 rings. The base of its inferior larynx is sustained by a cartilage 

 which I have not met with in any other animal of this class; it is 

 a round, membranous, crenulated plate, upon which rises a small com- 

 pressed bone. The want of sacs in the lower end of the larynx, in the 

 Phasianus garruhts, is compensated by the mechanism of the superior 

 larynx. Above the opening of the trachea there is a rima leading to 

 two membranous pouches. In blowing through the bronchi into the 

 trachea, these pouches are seen to swell. Valves are also wanting in 

 the inferior larynx of the Pelecanus fuscus, but there are true sacs in 

 the superior. In the glottis of the Palamedea bispinosa, whose trachea 

 presents the extraordinary enlargement I have just described, there are 

 folds having some analogy with the sacs which in man form the 

 ligaments which go from the arytenoid cartilages to the thyroid. These 

 folds seem to modify the voice of this bird ; for in the inferior larynx, 

 which I opened and have carefully drawn, there is nothing which can 

 perform their functions. In the same class of animals, it is sometimes 

 the glottis, sometimes the form of the trachea, and sometimes the 

 inferior larynx, which modifies or gives character to the voice. 



I cannot leave this subject without adding a few words on the 

 formation of the os hyoides in parrots and pelicans, furnished with 

 an immense sac under the throat. The os hyoides of the Pelecanus 

 alcatras does not present small horns (cornua) anteriorly, but a 

 complicated structure. It is triangular, spur-shaped and terminated 



The os hyoides of Pelecanus alcatras. 



by a large osseous button. Towards the base of the triangle, between 

 the two large horns, is a bony member or branch, which I have not 

 seen in any other animal, and which appears like a minute middle 

 horn. I have carefully examined the tongue of parrots, to discover the 

 reason that several tribes, the Aras for example, never learn to imitate 



