THE LARYNX 419 



Musculus Thyreoarytaenoideus (O.T. Thyro-arytenoideus 

 Externus). This muscle also springs from the angle of union 

 of the two laminae of the thyreoid cartilage, in close associa- 

 tion with the vocalis. Its fibres pass posteriorly, and are 

 inserted into the lateral surface of the arytaenoid cartilage. 

 It protracts the arytaenoid cartilage, and adducts and relaxes 

 the vocal fold. 



Epiglottis --/ 



Ary-epiglotticus 



Tubercle of epiglottis -'- 



Ventricular fold 

 Ventricle of larynx - 



Vocal fold -V- 

 Musculus vocalis 

 Lateral crico-arytaenoideus" 



Crico-thyreoid muscle 



Cricoid cartilage J 



Trachea 



FIG. 164. Frontal section of Larynx showing Muscles. 



Dissection. The lateral crico-arytsenoid muscle should now be carefully 

 removed, and at the same time the dissector should endeavour to disengage 

 the fibres of the thyreo - arytaenoideus from the deeper musculus vocalis, 

 in order that the relation of the latter to the vocal ligament may be 

 studied. Finally remove the musculus vocalis. This will display the outer 

 surface of the conus elasticus, the vocal ligament, and the wall of the laryn- 

 geal ventricle. By carefully dissecting between the two layers of mucous 

 membrane which form the ventricular fold, the weak ventricular ligament, 

 which gives it support, maybe discovered, as well as a number of racemose 

 glands which lie in relation to it. 



Ligamentum Vocale. This ligament is the thickened 

 free border of the lateral part of the conus elasticus, and it 

 constitutes the support of the vocal fold. It is attached, 

 anteriorly, close to its fellow of the opposite side, to the 

 middle of the angular depression between the two laminae of 



