THB LABYm 453 



tho superior is attached to tho inferior border of the arytcnoid cartiluu'. . 

 towards the angle which separates this from the posterior border. The 

 articulation of sounds is principally due to tho vibration of these cords. 



F. Tho epiglottis is fixed by amphiarthrosis to the body of the thyroid 

 cartilage, by means of clastic fasciculi mixed with fat, which pass from the 

 base of the first to the upper face of tho second. It is not rare to find among 

 these fasciculi small synovial bursae. 



G. The epiglottis is united, laterally, to tho inferior border of tho 

 arytenoids, through the medium of the two mucous folds already noticed, in 

 tho substance of which are the cartilaginous prolongations annexed to tho 

 base of this fibro-cartilage. These prolongations circumscribe, anteriorly, 

 the ventricles of the larynx, and are sometimes designated the superior vocal 

 i-or<l$ : a name we rarely give them, as they do not merit it. 



H. Finally, the first ring of the trachea is attached to the cricoid 

 cartilage by a circular elastic membrane. 



All of thesg articulations have neither tho same importance nor mobility. 

 The kind of movements they permit is easily understood, and they are suf- 

 ficiently indicated in the description of tho muscles which execute them. 



It is sufficient here to state, that these movements may either produce 

 the shortening or elongation of the larynx, its dilatation or contraction in a 

 transverse direction, or the occlusion of its anterior opening. 



2. Muscles of the larynx. The laryngcal apparatus is elevated or 

 depressed with the hyoid bone, which it follows in all its movements. It 

 is also moved by proper muscles, which either produceits total displacement, 

 or cause the several pieces of its cartilaginous framework to play upon each 

 other. Among these muscles there are three extrinsic : tho kterno-thyroideus, 

 Injo-tlnjmidcm, and the hyo-epiglottideus. The others are intrinsic, or 

 attached in their origin and termination to the different pieces of the larynx ; 

 they are : tho cnco-thyroid, posterior crico-arytenoid, lateral crico-aryteiioid, 

 tkfro-erytenoid, and the arytenoidem muscles. All are pairs, except the last 

 and tho hyo epiglottideus. 



STERNO-THYHOIDEUS. (See page 198.) 



HYO-THYROIDEUS. This is a wide, triangular muscle formod entirely of 

 muscular fasciculi, which originate from tho whole extent of the hyoid 

 conm, and terminate on tho external face of the thyroid ala; the most 

 inferior are longest. This muscle covers tho thyroid cartilage and the 

 thyro-hyoid membrane. It is covered by tho maxillary gland. 



In contracting, this muscle brings the thyroid cartilage within tho branches 

 of tho hyoid bone, and in this way carries tho larynx forward and upward. 



HYO-EPIGLOTTIDECS. By this name is designated a small cylindrical 

 fasciculus, whose fibres are buried in tho middle of a mass of adipose tissue, 

 and which extend from the superior face of tho body of the hyoid bone to tho 

 ant< To-inferior face of the epiglottis. Partly covered by tho mucous 

 membrane of the pharynx, this muscle concurs in restoring tho epiglottis 

 to its normal position after tho passage of the alimentary bolus. But it is 

 also necessary to state that tho epiglottis is carried forward more particularly 

 by its own proper elasticity, as well as that of tho ligamentous fasciculi 

 which attach it to the thyroid cartilage. 



Citico-THYBOiDEDs (Fig. 229, 8). This small muscle, applied to the 

 external side of tho cricoid cartilage, is elongated from above to below, 

 !inl composed of strongly tendinous fibres which cross, more or li-s-;. the 

 genor.il din -ction of the muscle. They arise from the above-named cartilage, 

 and pass to tin posterior border of the thyroid plate. 



