MUSCLES OF THE LARYNX. 531 



edge, runs obliquely upward and backward, and is in- 

 serted into the base of the arytenoid. Function. To draw 

 the arytenoids outward, and enlarge the rima glottidis, as 

 in inspiration. This is a dilator muscle. 



Arytenoideus obliquus (Fig. 164J arises from the base of 

 one arytenoid cartilage, and is inserted into the apex of 

 the other. Its fibres are small and sometimes absent, and 

 it is described by some anatomists as forming a part of the 

 next muscle. 



The arytenoideus transversus (Fig. 164) arises from the 

 posterior surface of the one arytenoid cartilage, and runs 

 transversely to be, inserted at a similar point on the other, 

 and filling up the concavities of each. This is a single 

 muscle. 



Function. Both these latter muscles bring the aryte- 

 noids together, and thus close the glottis, being thereby 

 constrictors of this opening. 



The tliyro-epiglottideus has indistinct fibres, which arise 

 from the inner angle of the thyroid cartilage, and are 

 inserted into the base and side of the epiglottis. 



Function. To draw down the epiglottis. 



Aryteno-epiglottideus. The fibres of this muscle are also 

 indistinct. It arises from the superior extremities of the 

 arytenoid cartilages, and passes forward and upward to be 

 inserted into the sides of the epiglottis. Function. The 

 same as the latter muscle. 



An inferior aryteno-epiglottidean muscle is spoken of by 

 Mr. Hilton, as arising from the arytenoid cartilage above 

 the vocal chords, and thence proceeding forward, over the 

 sacculus laryngis, to be inserted into the side of the epiglot- 

 tis. Its use, he thinks, is to diminish the cavity of this 

 sac, and compress the adjacent mucous glands. 



The conjoint action of all these muscles tends harmoni- 

 ously to one common end the production of voice ; and 

 although, to a considerable extent, they are voluntary, 

 nevertheless the will has not perfect command over their 

 separate actions; and, says Mr. Harrison, "those fibres 

 which are connected with the epiglottis, and which proba- 



