THE PRODUCTION OF THE VOICE. 



530 



movements of either of these cartilages must produce an effect on them of 

 some kind or other. Inasmuch, too, as the arytenoid cartilages rest on the 

 top of the back portion of the cricoid cartilage, and are connected with it by 

 capsular and other ligaments, all movements of the cricoid cartilage must 

 move the arytenoid cartilages, and also produce an effect on the vocal cords. 



Intrinsic Muscles. The intrinsic muscles of the larynx are so connected 

 with the laryngeal cartilages that by their contraction alterations in the con- 

 dition of the vocal cords and glottis are produced. They are usually divided 

 into four classes according to their action, viz., into abductors, adductors, 

 sphincters, and tensors. The Abductors, the crico-arytenoidei, widen the glottis, 

 by separating the cords ; the Adductors, consisting of the thyro-ary-epiglottici, 

 the arytenoideus posticus sen transversus, the thyro-arytenoidei externi, the crico- 

 arytenoidei laterales, and the thyro-arytenoidei interni, approximate the vocal 

 cords, diminish the rima glottidis, and act generally as Sphincters and sup- 

 porters of the glottis. Finally, the Tensors of the cords put the cords on the 

 stretch, with or without elongating them ; the tensors are the crico-thyroidei 

 and the thyro-arytenoidei interni. 



The attachments and the action of the muscles will be readily understood 

 from the following table. All the muscles are in pairs except the arytenoideus 

 posticus. 



TABLE OF THE SEVERAL GROUPS OF THE INTRINSIC MUSCLES OF THE LARYNX 



AND THEIR ATTACHMENTS. 



GROUP. 



MUSCLE. 



ATTACHMENTS. 



ACTION. 



I. 

 Abductors. 



Crico-aryte- 

 noidei pos- 

 tici. 



This pair of muscles arises, on 

 either side, from the posterior 

 surface of the corresponding half 

 of the cricoid cartilage. From 

 this depression their fibres con- 

 verge on either side upward and 

 outward to be inserted into the 

 outer angle of the base of the 

 arytenoid cartilages behind the 

 crico-arytenoid laterales. 



Draw inward and 

 backward the 

 outer angle o f 

 arytenoid carti- 

 lages, and so ro- 

 tate outward 

 the processus vo- 

 calis and widen 

 the glottis. 



II. and III. 

 Adductors 



and 

 Sphincters. 



[n three lay- 

 ers : 



(a) Outer 

 layer, Thy- 

 ro - ary - 

 e p i g 1 ot- 

 tici. 



A pair of muscles. Flat and nar- 

 row, which arise on either side 

 from the processus muscularis of 

 the arytenoid cartilage, then pass- 

 ing upward and inward cross 

 one another in the middle line to 

 be inserted into the upper half of 

 the lateral border of the opposite 

 arytenoid cartilage and the poste- 

 rior border of the cartilage of 

 Santorini. The lower fibres run 

 forward and downward to be 

 inserted into the thyroid carti- 

 lage near the commissure. The 

 fibres attached to the cartilage of 

 Santorini are continued forward 

 and upward into the ary-epiglot- 

 tic fold. 



Help to narrow or 

 close the rima 

 glottidis. 



