354 



ACTION OF THE VOCAL ORGANS. 



Fig. 181. 



of larynx. 



Posterior view of 

 larynx. 



thyroid cartilage, united to, t, the great horn of the os hy- 

 oides by, &, the lateral thyro-hyoid ligament ; Z, thyro-hyoid 

 membrane, traversed by the superior laryngeal nerve ; m, 

 posterior crico-arytenoid muscle ; ft, lateral crico-arytenoid ; 

 1, inferior laryngeal nerve; 2, posterior crico-arytenoid 

 twigs ; 3, lateral crico-arytenoid twigs ; 4, thyro-arytenoid 

 twigs ; 5, arytenoid twig. 



Fig. 182 is the posterior view of the lar- 

 ynx : a, base of the tongue ; , posterior bor- 

 der of the thyroid cartilage ; c, <?, thyroid body ; d, pos- 

 terior crico-arytenoid muscle ; 0, arytenoid muscle ; 1,1, 

 superior laryngeal, traversing the superior thyro-hyoid 

 membrane, and giving off lingual and epiglottic branches, 

 and others to the mucous membrane covering the poste- 

 rior face of the larynx ; 2, twig for the arytenoid muscle ; 

 3, anastomotic of Galien ; 4, inferior laryngeal ; 5, tra- 

 cheal branches ; 6, twig for the posterior crico-arytenoid 

 muscle ; 7, twig for the arytenoid muscle ; 8, branch for the lateral crico- 

 arytenoid and posterior crico-arytenoid muscles. 



The researches of Miiller furnish the best account we possess of the 

 Midler's ex- action of the vocal organs. He has shown that the larynx 

 the action of the * s essentially a reed instrument with a double membranous 

 vocal organs, tongue. That the rima glottidis is the seat of the origin of 

 the sound is proved by the fact that when an aperture exists in the tra- 

 chea below the glottis the voice disappears, but if above the glottis there 

 is no effect. Magendie records the case of a man who had a fistulous 

 opening in his trachea, and who could not speak unless he closed it or 

 wore a tight cravat. Moreover, the human or animal larynx can be made 

 to produce its characteristic sounds with more or less distinctness, after it 

 has been removed from the body, by directing a current of air through 

 the trachea. Cases have occurred which have afforded the opportunity 

 of observing the condition of the glottis while emitting sounds. The 

 vocal cords are brought into parallelism with one another, and separated 

 by an interval of scarcely more than from the y^ to the y|^ of an inch ; 

 but when the air is moving in and out silently, the fissure assumes a di- 

 vergent or triangular form. 



Professor Miiller gives the following account of the mode of produc- 

 tion of the notes of the natural voice. " The vocal ligaments vibrate in 

 their entire length, and with them the surrounding membranes and the 

 thyro-arytenoid muscles. For the deepest notes, the vocal ligaments are 

 much relaxed by the approximation of the thyroid to the arytenoid car- 

 tilages. The lips of the glottis are, in this state of the larynx, not only 

 quite devoid of tension j they are, when at rest, even wrinkled and pli- 



