VOICE OF REPTILES. - The mechanism of the vocal organs in reptiles presents very diver sified forms. The larynx varies considerably in structure, not only in different orders, but in different genera of the same family. It would therefore be impossible to compress within the limits assigned to this article the 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 arytenoid 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 Quadrumana. 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 cam eleon, than in the crocodile. They are broad membranous folds passing from the bases of the arytenoid car tilages to the inner surface 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 Sauna. In the Emys, and the Testudo, 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. Grceca and several other species. The muscles of the larynx are the constrictor, and the dilator aditus laryngis.
Ophidia. —In this class the larynx is 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.