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TEXT-BOOK OF PHYSIOLOGY. 



to be inserted into the anterior surface and external angle of the 

 arytenoid cartilage. The inner portion of the muscle lies close to 

 and supports, if it does not constitute a part of, the vocal band. 

 The action of tfie thyro-arytenoid muscle in conjunction with the 

 lateral crico-arytenoid is to rotate the arytenoid cartilage around 

 the vertical axis and to draw the vocal process forward and inward, 

 thus carrying the vocal cord toward the median line. When the 

 muscles of the two sides simultaneously contract, the vocal bands 

 are closely approximated and the space between them, the rim a 

 vocalis, reduced to a mere slit, one of the conditions essential to 

 phonation (Fig. 266). 



The arytenoid muscle consists (i) of transversely arranged fibers 

 which arise from and are inserted into the outer surface of the oppo- 



FIG. 265. GLOTTIS WIDELY OPENED 

 FROM SIMULTANEOUS CONTRACTION 

 OF BOTH CRICO-ARYTENOID MUS- 

 CLES, b. Epiglottis. rs. False 

 vocal band. ri. True vocal band. 

 ar. Arytenoid cartilages, a. Space 

 between the arytenoids. c. Cunei- 

 form cartilages, ir. Interarytenoid 

 fold. rap. Aryepiglottic fold. cr. 

 Cartilage rings. (Mandl.} 



FIG. 266. POSITION OF THE VOCAL 

 BANDS DUE TO THE SIMULTANEOUS 

 CONTRACTION OF BOTH LATERAL 

 CRICO-ARYTENOID MUSCLES AND 

 BOTH THYRO-ARYTENOID MUSCLES. 

 b. Epiglottis, rs. False vocal band. 

 ri. True vocal band. or. Space be- 

 tween the arytenoid cartilages, the 

 glottis respiratoria. ar. Arytenoid 

 cartilages, c. Cuneiform cartilages. 

 rap. Aryepiglottic fold. ir. Interary- 

 tenoid fold. (Mandl.) 



site arytenoid cartilages, and (2) of obliquely directed fibers which 

 arise from the outer angle of one arytenoid to be inserted into the 

 apex of the other. In their course they decussate in the median 

 line. The action of this muscle is to approximate the arytenoid 

 cartilages and thus obliterate that portion of the glottis between the 

 vocal processes, the rima respiratoria, and so direct the expiratory 

 blast of air toward and through the rima vocalis. 



The collective actions of the three foregoing muscles is to close 'or 

 constrict the glottis, and for this reason they are spoken of as the 

 adductor or phonatory muscles. 



The crico-thyroid muscle arises from the side and front of the 

 cricoid cartilage and is inserted above into the lower border of the 

 thyroid cartilage. The action of this muscle is to draw up the an- 

 terior part of the cricoid cartilage toward the thyroid, which remains 



