438 



VOICE AND SPEECH 



Arytenoid Muscle. This single muscle fills the space between the 

 arytenoid cartilages and is attached to their posterior surfaces and bor- 

 ders. Its action is to approximate the posterior extremities of the chords 

 and to constrict the glottis, so far as the articulations of the arytenoid 

 cartilage with the cricoid will permit. This muscle is important in 

 phonation, as it serves to fix the posterior attachments of the vocal 



chords and to increase the efficiency of 

 certain other of the intrinsic muscles. 



L at era I Crico-arytenoid Muscles. These 

 muscles are in the interior of the larynx. 

 They arise from the sides and superior 

 borders of the cricoid cartilage, pass up- 

 ward and backward and are attached to 

 the base of the arytenoid cartilages. By 

 dividing all the filaments of the recurrent 

 laryngeal nerves except those distributed 

 to these muscles and then stimulating the 

 nerves, it is shown that they act to approxi- 

 mate the vocal chords and constrict the 

 glottis, particularly in its interligamentous 

 portion. These muscles, with the aryte- 

 noid, act as constrictors of the larynx. 



Thyro-arytenoid Muscles. These mus- 

 Fig. &.- Lateral view of the muscles cles are situated within the larynx. They 

 of the larynx (Sappey). are broad and flat and arise in front from 



i, body of the hyoid bone; 2, vertical fo e upper part of the crico-thvroid mem- 



section of the thyroid cartilage ; 3, hori- 



zontal section of the thyroid cartilage, brane and the lower half of the thyroid 



turned downward to show the deep carti l age . From fo is Hne Q f origin each 



attachment of the crico-thyroid muscle ; 



4, facet of articulation of the small cornu muscle paSSCS backward in two fasciculi, 



both being attached to the anterior sur- 



10, arytenoid muscle; n, aryteno-epi- 



giottidean muscle; 12, middle thyro- 

 ment '' I3> 



tiiage; 6. superior attachment of the f a ce and the outer borders of the arytenoid 



crico-thyroid muscle ; 7, posterior crico- ,., <-, . , . ,. - 



arytenoid muscle; 8, lateral crico-aryte- Cartilages. Stimulation of the nCFVOUS 



noid muscle; 9, thyro-arytenoid muscle; figments distributed to these muscles 



renders the vocal chords ten se. Ihevana- 

 thyro ' hyoid tions that may be produced in the pitch 



and quality of the voice by the action 

 of muscles operating directly or indirectly on the vocal chords render 

 the problem of the precise mode of action of the intrinsic muscles 

 of the larynx complicated and difficult. It is certain, however, that 

 in these muscular acts, the thyro-arytenoids play an important part. 

 Their contraction regulates the thickness of the chords, while at the 

 same time it modifies their tension. The swelling of the chords, which 



