GLOTTIS. VOCAL CORDS. 23! 



whether we see the whole or only the two anterior thirds. 

 This opening permits the passage of the air into and out of 

 the chest, it is called the glottis, the folds which circumscribe 

 it have been called the vocal cords. About one-third of an 

 inch higher up there are two other similar but less prominent 

 folds, they are formed by the superior thyro-arytenoid liga- 

 ments, and are designated by this name, or by that of the 

 superior vocal cords (see fig. 44, p. 229). The space between 

 them has been called the superior glottis, it is larger than the 

 glottis proper, and does not resemble it in form when exam- 

 ined by the aid of the laryngoscope. Before this instrument 

 was invented the larynx was described by anatomists as they 

 saw it in the dissecting-room, hence the name of superior 

 glottis, and the likening of this orifice to that of the glottis. 



Between the vocal cords proper and the superior thyro- 

 arytenoid ligaments there is on each side a depression; these 

 are the ventricles of the larynx; and lastly, a little above these 

 ligaments is the stiperior opening of the larynx, surmounted in 

 front by the epiglottis, which is lowered upon, and covers it 

 completely during deglutition. The space comprised between 

 the glottis and the superior opening of the larynx is called 

 the vestibule of the glottis. 



Formerly authors were divided in opinion in regard to the 

 larynx; some gave the name of glottis to all the region 

 between the level of the inferior and that of the superior 

 vocal cords, others applied it to the superior glottis, and 

 others again to the inferior glottis only. This last opinion, 

 which has been commonly received since the investigations of 

 Bichat and Boyer, has been confirmed by the laryngoscope, 

 which demonstrates the existence of a single glottis, and a 

 single pair of vocal cords. 



The internal walls of the larynx are lined with a fibrous 

 membrane, constituted in part by yellow elastic tissue. This 

 membrane, which forms the thyro-arytenoid and aryteno-epi- 

 glottic ligaments, is covered throughout its whole extent by 

 a mucous membrane, which on the free border of the vocal 

 cords is very thin and transparent, slightly adherent, and 

 covered with an epithelium different from that found on the 

 rest of its surface. 



