MUSCLES OF THE LARYNX. 



289 



The crico-thyroicl muscle (fig. 193, 10), is a short thick triangular 

 muscle, seen on the front of the larynx. Its origin from the cricoid 

 cartila"-e, extends from the median line a considerable way backwards, 

 and its fibres passing upwards and outwards, diverging slightly, are 



Fig. 193. 



Fig. 193.— Lateral View of the Cartilages of the Larynx with the Crico-Thyroid 

 Muscle (after Willis). 

 8, tliyroid cartilage ; 9, cricoid ; 10, crico-tliyroid muscle ; 11, crico-tliyroid mem- 

 brane ; 12, upper rings of the trachea. 



Fig. 194.— View of the Lary:<x and Part of the Trachea from behind, with the 



Muscles dissected. 

 li, the body of the hyoid bone ; c, epiglottis ; t, the posterior borders of the thyroid 

 cartilage ; c, the median ridge of the cricoid ; a, arytenoid muscle ; s, placed on one 

 of the oblique fasciculi ; h, left posterior crico-aryteuoid muscle ; r, ends of the incom- 

 plete cartilaginous rings of the trachea ; /, fibrous membrane crossing the back of the 

 trachea ; n, muscular fibres exj)osed in a part. 



_inse rted into the inferior border of the thyroid cartilage, and into the 

 anterior border of its lower cornu. The lower portion of the muscle, 

 the fibres of wliich, nearly horizontal, are inserted into the lower cornu, 

 is usually distinct from the rest. Some of the superficial fibres are 

 almost always continuous with the inferior constrictor of the pharynx. 

 The muscles of the two sides separate from one another iu the middle 

 line in front, leaving an interval which is triangular with the base 

 upwards. The crico-thyroid membrane is here uncovered. 



The posterior crico-arsrbenoid m-ascle (fig. 194, l), situated be 

 hind , arises from the broad depression on the corresponding half of 

 the posterior surface of the cricoid cartilage, and its fibres, converging 

 upwards and outwards, are inserted mto the outer angle of the base of 

 the arytenoid cartilage, beliind the attachment of the lateral crico- 

 arytenoid muscle. The upper fibres are short and almost horizontal ; 



VOL. II. u 



