1496 



VOICE. 



teriorly by the thyroid, laterally by the ary- 

 tenoids, and posteriorly by the cricoid carti- 

 lage, but is destitute of salient membranous 

 laminae. * 



Muscles. The superior larynx is raised 

 by the hyo-thyroideus and the thyro-tra- 

 chealis muscles, and depressed by the hypsilo 

 and sterno-trachealis. The glottis is opened 

 by the thyro-arytenoideus posticus, and closed 

 by the thyro-arytenoideus lateralis, as in the 

 higher order of reptiles. 



The superior larynx is supplied by the 

 superior laryngeal nerve alone, the inferior 

 laryngeal terminating in the inferior larynx 

 and trachea. 



The inferior larynx. This organ is pecu- 

 liar to birds. It is exceedingly diversified in 

 form and structure. It is always found except 

 in the condor, and other vultures. If \ve make 

 a section of the lower larynx of birds in the 

 mesial plane, its lateral segments, if viewed 

 separately, present a double organ of sound ; 

 the exceptions to this rule are, the parrot, 

 perroquet, and cockatoo. The inferior larynx 

 of birds is often a very complex structure, and 

 may be considered a double reed furnished 

 with a pipe. It is symmetrical in most orders 

 of birds except the Palmipedes, and is situated 

 between the last ring of the trachea and first 

 of the bronchi; it lies upon the oesophagus pos- 

 teriorly, where there is generally a triangular 

 space for the passage of that tube. 



The frame-work of the inferior larynx is 

 formed by the developement of several lower 

 rings of the trachea, which take diversified 

 forms in different orders of birds, and some- 

 times in the sub-genera of the same order, as 

 in Mergus and Anns among the Palmipedes. 

 In those birds which have a pure quality of 

 voice, and whose instinct excites them to pro- 

 duce a continuous succession of tones, con- 

 stituting some defined melody, we find the 



* Although anatomists are generally agreed respect- 

 ing the position and figure of the several pieces which 

 enter into the formation of the superior larynx of 

 birds, they differ widely in reference to the parts 

 which they represent when compared with man. 

 Cuvier conceives that the posterior cartilage, which 

 Humboldt l calls sockel, represents the cricoid of 

 Mammalia, and that birds are destitute of epiglottis, 

 thyroid, and arytenoid cartilages. Fabricius 2 con- 

 siders it best to divide the pieces into three parts, 

 viz. two arytenoids and an os-innominatum. Tiede- 

 mann 3 thinks the anterior piece represents the 

 thyroid, the quadrangular pieces the cricoid, and 

 the triangular the arytenoid cartilages of Mamma- 

 lia. Meckel 4 , on the contrary, considers the trian- 

 gular pieces to be the cricoid divided. Cams 5 

 siipposes the quadrangular pieces to be arytenoids, 

 and the triangular the cartilages of Santorini. 

 Wagner 6 unites the single with the quadrilateral 

 pieces for a cricoid, and the triangular for the 

 arytenoids. 



1 Observations de Zoologie. 



3 De Larynge. P. i. cap. vii. In op. omnia. Lips. 

 16_87, p. 273. 

 5 Zoologie, b. ii. p. 644. 

 * Archiv. fur Anat. und Physiol. 1832, p. 324. 



5 Lehrbuch der Vergleichenden Zootomie, b. i. 

 p. 195. 



6 Lehrbuch der Vergleichenden Anatomic, p. 242. 



inferior larynx not only better adapted to pro- 

 duce a purer quality of tone, but it is pro- 

 vided with a greater number of muscles for 

 modulating the voice. 



Among the Insessores, the Corvidae and 

 Sylviadae have the external walls of the infe- 

 rior larynx composed on each side of three 

 semilunar bones which are developed from 

 the inferior portion ot the trachea. The larynx 

 is bounded internally by a bone, which tra- 

 verses the lower end of the trachea, the verti- 

 cal longitudinal section of which coincides with 

 the plane of the mesial section i (^g. 912): 

 this os transversale, after stretching across 

 the tube, divides at each end into two lamina?, 

 which diverge laterally from the axis of the 

 bone to meet the two first external bones of 

 the larynx, thus strengthening and complet- 

 ing its solid framework. The superior part 

 of the os transversale is concave, and fur- 

 nished with a very thin delicate membrane, 

 rising vertically from the bone // (fig. 912): 

 this is called by Savart the membrana semi- 

 lunaris* 



Fig. 912. 



Section of tJie lower Larynx. 



h. membrana semilunaris ; i, os transversale ; g, 

 membrana tympaniformis. 



This membrane is most developed in sing- 

 ing birds, and is considered hy Savart to be 

 one of the most essential organs ot'voice in the 

 inferior larynges of the nightingales, thrushes, 

 linnets, finches, and other singing birds, as 

 well as in speaking birds, such as the pies, 

 jays, &c. The inferior edge of the os trans- 

 versale gives attachment to the membrana tym- 

 paniformis. 



Bones of the inferior larynx. The first 

 bone a (fig. 913) is flattened and curved, 

 being convex externally, and concave inter- 

 nally: it forms the boundary of the internal 

 lateral face of the larynx. 



The second bone b (fig. 913) presents nearly 

 the same form as the first, but it possesses 

 greater mobility, the muscles which are in- 

 serted into it drawing it upwards and out- 



