LARYNX OF .MAM MALTA. 



001 



47o 



ward, ib. c, below the basihyal, ib. b, which was slightly expanded 

 and excavated for its reception. In the larger species of Tro- 

 glodytes ( Tr. Gorilla), this sacculus is developed in the adult 

 male to the degree which it presents in Pithecus Satyrus. The 

 roar of the male Gorilla is loud, and may be heard far off in its 

 native forests. 



In Man there is no such excess of development of the laryngeal 

 sacculi or other part of the vocal organ. The cords are long 

 and well-defined, and all parts of the organ are in well-balanced 

 proportion. The chief elements 

 of the vocal organ have been 

 already defined and exemplified 

 in figures 453 and 454. The 

 external muscles of the larynx, 

 viz., the e thyro-hyoidei,' 'sterno- 

 thyroidei,' and ' crico-thyroidei,' 

 operate (among other actions) in 

 producing that rotation of the 

 cricoid upon the thyroid which 

 effects the important change in 

 the angle of the vocal cords as 

 it exists in ordinary breathing, 

 when they are so inclined to each 

 other as to have no vibratory 

 motion, to the position in which 

 their surfaces lie in the same 

 plane, and when the breath ex- 

 cites their vibration ; the ( thyro- 

 arytenoidei,' fig. 477, d, d' ', co- 

 operate in putting the cords into 

 this position. The quality of the vibration dependent upon the 

 degrees of tension of the vocal cords, and the vocal tones due to 

 degrees of patency of the ( rima glottidis,' are mainly influenced 

 by muscles acting upon the cords, fig. 476, c, c, through the 

 medium of the arytenoid cartilages, b, b. If the left wing of 

 the thyroid be removed, the following muscles operating on the 

 vocal cords through that medium may be demonstrated. To 

 each arytenoid cartilage proceeds a pair of muscles ; one, ' thyro- 

 arytenoideus,' fig. 477, d, arises from the inner surface of the 

 anterior part or angle of the thyroid a: the superior fibres, 

 a", pass horizontally backward and outward to be attached to 

 the prominence on the outer side of the arytenoid, 7; these, 

 sometimes distinguished as the i thyro-arytenoideus superior,' 



Larynx of Chimpanzee. 



