338 HUMBOLDT ON THE ORGANS OF THE VOICE. 



sky, becomes, in consequence of its radiation, colder than the surround- 

 ing air. Under these circumstances, the air deposits a portion of its 

 humidity on the cold surface of the body, which is neither more or less 

 than the phenomenon of dew, as analysed by Dr. Wells. Now animal 

 substances become much sooner putrid when moist than when dry* 

 The observation of Pliny and Plutarch is therefore correct in all its 

 details. It was only necessary to reform the theory, and acquit the 

 moon of the mischief ascribed to her. 



Of all known substances the chloride of silver is that of which the 

 colour suffers the greatest and most rapid change on exposure to light. 

 But a plate of this chemical compound, exposed for a long time to the 

 light of the moon, condensed in the focus of a powerful burning glass, 

 is observed to lose nothing of its primitive whiteness. 



ON THE ORGANS OF THE VOICE IN BIRDS AND MONKEYS. 



BY BARON HUMBOLDT. 



THERE is a great difference in the construction of the larynx in 

 those animals which have an epiglottis and in those which have none. 

 In the latter we do not find any thing resembling the cricoid and thy- 

 roid cartilages of the larynx of mammiferae. In the amphibia, the 

 glottis is situated in a round fleshy mass (bourreleC), formed by the in- 

 terweaving of nearly circular fibres : in birds it is cartilaginous, almost 

 osseous, and tolerably uniform in its external form. In the genera 

 Pelecanus, Phasianus, Ardea, and Phcenicopterus, the larynx has a 

 triangular shape, the apex of the triangle being directed forwards, and 

 its base or posterior part being fringed with little pointed, white, carti- 

 laginous teeth. These tubercles, which border the glottis, are very 

 broad and short in Phasianus paraka of the Orinoco, they form a white 

 band in the Ardea cocoes ; they cover, almost entirely, the glottis of the 

 Palamedea bispinosa, and that also of the Aras, a family of the parrot 

 tribe ; but they are entirely wanting in some aquatic birds, as in the 

 alkatras of the South Sea. The six designs in which I have represented 

 the larynx of birds, present all these varieties of construction. The 

 glottis is supported at its base by an osseous, broad, flat cartilage, 

 sometimes crenated anteriorly, as in the Guyana pheasant, but pointed 

 and elongated in the pelicans and Phcenicopterus. 



