528 



ANATOMY OF VERTEBRATES. 



351 



they are more acute-angled and directed backward. In the Toad 



(Bnfo) the chordae vocales are thin 

 elastic membranes, and in two pairs, fig. 

 351, a and b : the sacculi are seen to be 

 lodged in the large arytenoid cartilages. 

 The males of the common and edible 

 Frogs (Rana) have two submandibular 

 sacs, the male Tree-Frog (Hyla) has 

 one such sac, opening by a straight canal 

 into the larynx, and susceptible of con- 

 siderable distension by air during the 

 croak. All these diversities of laryngeal 

 structure affect the loudness, deepness, 

 or sharpness of the peculiar vocal notes 

 of Frogs and Toads. The air passes 



Larynx aud lungs (c, d) Toad, Bufo. tO the lungS, fig. 350, (/, 351, C, d, by 



short bronchi, fig. 350, f, save in the 



Pipa, in which the bronchial tubes are long, especially in the 

 female. 



The glottis in Serpents can be drawn forward and protruded 

 from the mouth by the action of the geniotrachedles muscles, 

 fig. 147, y, p. 229. In marine serpents the glottis is situated 

 very near the forepart of the mouth, and the air can be inspired 

 at the surface without exposure of the jaws. The upper rings 

 of the trachea coalesce to form a cricothyroid cartilage, sending 

 forward two processes which represent the arytenoids in many 

 Ophidia ; but which are freely articulated therewith in the great 

 constrictors. The ' processus epiglotticus ' is subquadrate in 

 Boa. True ( chordae vocales ' are absent ; and the voice is 

 reduced to a hissing sound produced by the action of the expired 

 air upon the margins of the glottis. The rings of the trachea 

 are entire, and the trachea varies in length in different ser- 

 pents before it reaches the lung. Along this it continues, of 

 decreasing breadth, with portions of the rings, as if incrusted in 

 the pulmonary parietes, for an extent varying in different 

 serpents. 



In Lacertians a cricothyroid cartilage supports a pair of 

 arytenoid cartilages : in most there is a cartilaginous or osseous 

 ' processus epiglotticus,' which, in a few, coexists with an incom- 

 plete epiglottis. The mucous membrane of the glottis is reflected 

 over the arytenoids, forming a depression beneath them, and folds 

 with free margins : these ' vocal chords ' are broad in the Chame- 

 leon and Gecko, and stretch from the base of the arytenoid to the 



