230 THE HUMAN BODY. 



form the posterior and superior wall of the larynx, and come 

 together behind in the shape of the lip of a ewer; they arti- 

 culate with the cricoid cartilage, and are united to the thyroid 

 by muscles and ligaments. 



4. The epiglottis (epi, added to, glotta, the tongue) is a sort 

 of cartilaginous valve, very elastic and mobile, situated a 

 little below the base of the tongue, and attached to the supe- 

 rior border of the thyroid cartilage. Its function is to cover 

 exactly the superior opening of the larynx during deglutition, 

 so as to prevent the introduction of the food into the air- 

 passages. When the tongue is brought well forward, and 

 the base depressed, in some individuals the summit of the 

 epiglottis is visible. 



Numerous muscles attach the larynx to the sternum, to the 

 hyoid bone, and by this last to the shoulder-blade, to the 

 tongue, and to the lower jaw; these muscles are called ex- 

 trinsic^ and move the larynx as one piece. Others, called 

 intrinsic muscles of the larynx, combine to form its walls, 

 and to modify its diameter by acting on the cartilages, and 

 assist in the functions of the glottis. Lastly, the arytenoid 

 cartilages are united by ligaments to the epiglottis, or to the 

 thyroid cartilage; these last, the thyro-arytenoid ligaments 

 form, with the muscles of the same name and with the mucous 

 membrane, the vocal cords, of which we proceed to speak. 



The cavity of the larynx, or its internal surface, does not 

 correspond in form and dimensions with the external surface; 

 it is cylindrical at the bottom, triangular at the top; the 

 dimensions of the lower part are invariable, while those of 

 the upper portion, on the contrary, are variable in form, from 

 the mobility of the epiglottis, of the arytenoid cartilages, &c. 

 About the middle of its height the laryngeal cavity presents 

 on each side a fold formed by the thyro-arytenoid muscles and 

 lower ligaments of the same name, and the mucous mem- 

 brane; these resemble two ribbons of a white colour tinged 

 with rose, running horizontally from front to back, attached 

 by their external border and their extremities to the wall of 

 the larynx, free on the surface and internal border, leaving 

 an opening between them which is linear, elliptic, or trian- 

 gular, according to the moment when it is observed, and 



