334 HEAD AND NECK 



to be inserted into the anterior surface of the processus 

 muscularis of the arytaenoid cartilage. The superficial or 

 lateral surface of the muscle is covered by the lamina of the 

 thyreoid cartilage and the upper part of the crico-thyreoid 

 muscle; its deep surface is applied to the conus elasticus. 

 The lateral crico-arytomoid muscles are supplied by the 

 inferior laryngeal nerves. They are adductors of the vocal 

 folds. 



Musculus Thyreo-arytsenoideus (O.T. Thyro-arytenoideus 

 Externus). Each thyreo-arytaenoid muscle springs from the 

 angle of union of the two laminae of the thyreoid carti- 

 lage, in close association with the vocalis. Its fibres pass 

 backwards, and are inserted into the lateral surface of the 

 arytaenoid cartilage. It protracts the arytaenoid cartilage, 

 and adducts and relaxes the vocal fold. It is supplied by the 

 inferior laryngeal nerve. 



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 vocalis to the vocal ligament may be studied. Finally, 

 remove the musculus vocalis. When the muscles are removed, 

 the lateral surface of the conus elasticus, the vocal ligament, 

 and the wall of the laryngeal ventricle will be displayed. By 

 carefully dissecting between the two layers of mucous membrane 

 which form the ventricular fold, the dissector may find the weak 

 ventricular ligament, which supports the fold, as well as a 

 number of racemose glands which lie in relation to it. 



Musculus Thyreo - epiglotticus. Each thy reo - epiglottic 

 muscle springs from the thyreoid cartilage, immediately above 

 the corresponding musculus vocalis, with the upper border of 

 which it is more or less blended. Its fibres run backwards 

 and upwards, into the ary-epiglottic fold, where they blend 

 with the ary-epiglotticus, and they are inserted into the edge 

 of the lower half of the epiglottis. The thyreo-epiglottic 

 muscles depress the epiglottis. They are supplied by the 

 inferior laryngeal nerves. 



Musculus Vocalis. Each musculus vocalis is a sheet of 

 muscular fibres which springs, anteriorly, from the angle of 

 union of the two laminae of the thyreoid cartilage. It runs 

 backwards, along the ligamentum vocale and the upper part of 

 the conus elasticus, and is inserted into the lateral surface 

 of the vocal process and the anterior surface of the body 

 of the arytaenoid cartilage. Its lower fibres blend with the 



