1502 



VOICE. 



minute anatomy of the several species ; they 

 have been recently investigated and detailed 

 in a monograph by Henle. 



Sauria. In the Crocodile the larynx is com- 

 posed of three cartilages, namely, the thy- 

 roid and cricoid consolidated into one ring- 

 formed cartilage, called the thyro-cricoid, and 

 the two arytenoid cartilages. The basi-hyoid 

 element of the hyoid bone is expanded into a 

 disc ; and lies in front of the larynx, which it 

 protects and supports. The arytenoid car- 

 tilages are connected with the superior margin 

 of the thyro-cricoid by a membranous suture, 

 but nothing approaching to a joint furnished 

 with ligaments and synovial membrane is ob- 

 servable. The mucous membrane of the 

 larynx is reflected over the inferior margins 

 of the arjtenoid cartilages, and forms a deep 

 pouch beneath them, leaving a free fold with 

 a margin on each side; so that, when these 

 cartilages are brought near each other, this 

 fold forms the vocal cord, and produces the 

 tones peculiar to the Alligators In the Ca- 

 meleon the larynx is provided with a sac in 

 front, similar to that observed in some of the 

 Quadrumaua. The air passes to and from 

 this sac by means of an opening, lying between 

 the lower margin of the larynx and the first 

 ring of the trachea. The larynx of this ani- 

 mal has been very minutely described by 

 Treviranus. 



Some reptiles have a membrane at the base 

 of the tongue, which answers to the epiglottis ; 

 others have a cartilaginous epiglottis ; others 

 again a mere bony or cartilaginous processus 

 epiglotticus, as in birds. " But," observes 

 Henle, " the presence of this process does 

 not imply that there is no epiglottis, or con- 

 versely, the presence of an epiglottis that there 

 is no processus epiglotticus." Cuvier de- 

 scribed five cartilages in the larynx of the 

 crocodile, but it is now generally admitted 

 that he was mistaken. 



The vocal cords are more perfectly deve- 

 loped in the Gecko, and the cameleon, than in the 

 crocodile. They are broad membranous folds 

 passing from the bases of the arytenoid car- 

 tilages to the innersurface of the crico-thyroid. 



In the Lacerta a very thin membranous fold 

 is found passing from the bases of these car- 

 tilages in the position of the vocal ligaments ; 

 but Henle is of opinion that the acute chirp- 

 ing tone of the lizard depends rather on the 

 vibration of the margins of the glottis, than 

 on these folds, which are incapable of being 

 approximated to each other, or brought into 

 a state of tension. 



Chelonia. The vocal organs of the Chelonia 

 are not adapted for perfect intonation of the 

 breath, being destitute of vocal cords. The 

 superior portion of the larynx is surrounded 

 by, and connected with the basi-hyoid element 

 of the os hyoides as in the Sauria. In the 

 Emi/x, and the Tesludo, the thyroid cartilage is 

 annular, and distinct from the cricoid ; the 

 arytenoids are triangular, and the internal 

 surface is much enlarged, owing to the very 

 concave form of the larynx. In the Midas, 

 the aditus laryngis is furnished with a fold of 



mucous membrane, which serves for the pro- 

 duction of certain sounds. In the great tor- 

 toise of Madagascar, Cuvier describes a tri- 

 angular membranous crest attached to the 

 base of the larynx which, ascending to its 

 opening, divides it into two parts, and is 

 analogous to what is found in the superior 

 larynx of some birds. Meckel found the same 

 kind of crest in T. tabulata, but it is absent 

 in T. GrtEca and several other species. The 

 muscles of the larynx are the constrictor, and 

 the dilator aditus laryngis. 



Ophidia. In this class the larynx i< very 

 little developed, with regard either to volume 

 or to mechanism. The upper rings of the 

 trachea are consolidated into a crico-thyroid 

 cartilage, to which the arytenoids are attached. 

 In some species these are sessile, mere pro- 

 cesses of the crico-thyroid ; and in others, they 

 are divided from it by a suture, but in the 

 pythons and boas they are free. The processus 

 epiglotticus is nearly quadrangular in the 

 Boa : the vocal cords are absent, and therefore 

 the voice is reduced to a mere hissing sound, 

 which is produced by the breath passing over 

 the edges of the aditus laryngis. The muscles 

 of the larynx are the elevator, depressor, di- 

 lator, and compressor laryngis. 



Batrachia. In the Batrachia the two 

 arytenoid cartilages form a considerable por- 

 tion of the frame of the larynx, and the cri- 

 coid, with a few exceptions, is a complete 

 ring. The arytenoids are triangular, and their 

 apices being upwards form the superior lateral 

 boundaries of the larynx. The vocal cords 

 pass from end to end of the bases of the 

 triangles. According to Henle, the whole of the 

 tailless Batrachia, except theP/jm and the Dac- 

 iylelhro, have vocal cords. In Bufo there are 

 two pairs of vocal cords (./?g. 9 19), correspond- 

 ing to the inferior vocal cords in Mammalia. 



Fig. 919. 



Bufo. 



a, and b, semilunar folds of the superior vocal 

 cord ; c. inferior vocal cord ; d, lung. 



Above and below the vocal cords there are sacs 

 lined with mucous membrane, and bounded by 

 the arytenoid cartilages. Between the vocal 

 cords a small cartilage is sometimes found. 



