246 THE VISCERA. 



The nasopharynx and pharynx are considered under the 

 alimentary canal (page 231). 



2. The Larynx. 



The larynx is the enlarged upper end of the air-passage 

 which leads from the pharynx to the lungs. It is a box com- 

 posed of pieces of cartilage connected by ligaments and moved 

 by muscles, and it is lined by mucous membrane. At the root 

 of the tongue about one centimeter caudad of the body of the 

 hyoid bone is the triangular leaf-like epiglottis (Fig. 95, c, 

 page 227). When food is taken this closes the opening into 

 the larynx, and the food passes over it into the oesophagus. 

 It is so curved that its apex is directed craniad. A fold of 

 mucous membrane, the plica glossoepiglottica or frenulum of 

 the epiglottis, extends from the middle of its cranial surface 

 to the root of the tongue, and on each side of this fold is a 

 depression. 



From each side of the base of the epiglottis a fold, plica 

 aryepiglottica (Fig. 95,/), extends caudad to the base of the 

 arytenoid cartilage {g). Dorsad of this fold and separated 

 from it by a depression is a ridge which marks the position of 

 the caudal hyoid cornu. The plica; aryepiglotticae (/) and the 

 epiglottis {/) form the boundaries of the aditus laryngis, or 

 opening into the larynx. 



The cavity of the larynx is divided into three portions. 

 The upper one of these is the vestibule of the larynx. It 

 is bounded caudad by two folds of mucosa (/') that stretch 

 from the caudal surface of the epiglottis near its base to the 

 tips of the arytenoid cartilages. These folds are the false 

 vocal cords (/). Their vibration is said to produce purring. 

 Caudad of the false vocal cords two folds of the mucosa 

 stretch from the apices of the arytenoid cartilages to the thyroid 

 cartilages, near the base of the epiglottis. These folds are 

 nearer the median plane than the false vocal cords. They 

 are the true vocal cords {J). The middle portion of the 

 laryngeal cavity is that between the true and the false vocal 

 cords. It is produced laterally into a very small pouch or 

 pocket on each side, the ventriculus. The narrow slit between 

 the true vocal cords is the glottis [h). It can be narrowed 



