THE LARYNX. 315 



(i) The M. dilatator aditus /aryw^e^ (Henle), (Fig. 205 i)./.) arises 

 on either side from the hinder end of the larg-er posterior eornu 

 of the hyoid : the fibres diverge slightly to be inserted into the 

 middle portion of the outer surface of the arytenoid cartilage; a 

 smaller bundle of fibres is attached to the deeper-lying constrictor 

 muscle and to the cricoid cartilage. 



(2) The M. constrictor aditus laryngis (Henle), (Fig. 205 C.aJ.), 

 arises on either side from the hinder half of the dorsal surface of 

 the posterior cornu of the hyoid. The two muscles enclose the larynx, 

 and are inserted into a median tendinous raphe on the under sur- 

 face of the larynx (//). The raphe is connected with the skeleton 

 of the larynx by connective-tissue. 



(3) The J/. Injo-anjtenoideus anterior(Fig. 205 C.oJ.) arises on each 

 side from the inner border of the anterior end of the cornu of the 

 hyoid ; the muscle lies close to the anterior border of the arytenoid 

 cartilage, and is inserted into a fibrous lamella on the dorsal surface 

 of the larynx. The M.petrohyoiâeus tertius is also partially inserted 

 into this lamella. 



(4) The M. petrohyoideus tertius (Fig. 205 fh^), (see also p. 66). 

 The greater part of this muscle is inserted into the end of the 

 posterior cornu of the hyoid {HR) ; a smaller portion {8, /S^) 

 is prolonged to be inserted into the cricoid cartilage and into the 

 fibrous lamella into which the MM. hyo-arytenoidei anteriores are 

 inserted. 



(5) The M. hyo-arytenoideus posterior (Fig. 205 C.o.l.^) arises on 

 each side from the superior angle of the corresponding arytenoid 

 cartilage, under cover of the tendon of the M. pjetrohyoidens tertius. 

 The muscle is inserted into the inferior angle of the arytenoid 

 cartilage. 



d. The interior of the larynx (Figs. 202, 2c6, 207). The cavity 

 of the larynx is constricted at two points : anteriorly it is con- 

 stricted by the true vocal cords (Figs. 206 V, 207 SB), posteriorly by 

 the false vocal cords. The whole cavity is Hned with mucous mem- 

 brane, which is continuous with that of the mouth anteriorly, with 

 that of the lungs posteriorly. 



(i) The true vocal cords are two vertical flat bands of con- 

 nective-tissue, attached above to the superior angles of the arytenoid 

 cartilages, below to their inferior angles ; their anterior borders are 

 thin and free ; near their posterior borders they are attached by 

 mucous membrane to the internal surfaces of the arytenoid cartilages. 



