232 THE VISCERA. 



nasopharynx is continuous craniad by the choanae with the 

 nasal cavity; it forms a horizontal tube between and ventrad 

 of the perpendicular plates of the palatine bones, and has the 

 same craniocaudal extent as the soft palate. Its dorsal \vall 

 lies against the bas'is cranii and the longus capitis muscles ; its 

 lateral walls against the pterygoid muscles and the perpendic- 

 ular plates of the palatine bones; its ventral wall is the soft 

 palate. At the middle of its length, at the junction of its 

 dorsal and lateral wall, are two longitudinal slits about three 

 millimeters long. These are the medial openings of the 

 Eustachian tubes, by which the nasopharynx communicates 

 with the tympanic cavity. 



The pharynx proper, situated caudad of the nasopharynx, 

 is smaller than the latter. It is bounded craniad by the 

 epiglottis and the margin of the soft palate, and is continuous 

 between the two, by the isthmus faucium, with the mouth 

 cavity. Its floor is formed by the cranial end of the larynx. 

 At its caudal end it passes dorsally into the oesophagus, while 

 ventrally it communicates with the larynx. Its walls are 

 muscular. 



MUSCLES OF THE PHARYNX (Fig. 96). M. glossopharyn- 

 geus (/). 



Origin. Some fibres on the ventral and lateral part of the 

 genioglossus (/) leave that muscle near its caudal end. They 

 form a thin band of diverging fibres which pass outside of the 

 cranial horn of the hyoid. A similar sheet of fibres leaves the 

 midventral part of the styloglossus (e). The two sheets unite 

 and the united muscle crosses the hyoid, turns dorsad, and has 

 its 



Insertion into the median dorsal raphe of the pharynx. 



Action. Constrictor of the pharynx. 



M. constrictor pharyngis inferior (k). A thin sheet of 

 muscle covering the sides of the pharynx at its caudal end. 



Origin from the lateral surfaces of the thyroid and the 

 cricoid cartilages. The fibres pass dorsad and craniad, the 

 cranial ones covering the fibres of the middle constrictor (/). 



Insertion. The median longitudinal raphe on the dorsum 

 of the pharynx. The caudal fibres are transverse and contin- 



