204 DIGESTION MASTICATION, INSALIVATION, DEGLUTITION. 



In Fig. 55, are shown the cavities of the mouth and pharynx with their 

 relations to the nares and the larynx. 



The isthmus of the fauces, or the strait through which the food passes 

 from the mouth to the pharynx, is bounded above, by the soft palate and the 

 uvula i laterally, by the pillars of the palate and the tonsils ; and below, by 



the base of the 

 tongue. 



The openings 

 into the pharynx 

 above are the pos- 

 fg terior nares and 

 20 the orifices of the 

 Eustachian tubes. 

 Below, are the 

 openings of the 

 esophagus and of 

 the larynx. 



The muscles of 

 the pharynx are 

 the superior con- 

 strictor, the stylo- 

 pharyngeus, the 

 middle constrictor 

 and the inferior 

 constrictor ; and 

 it is easy to see, 

 from the situation 

 of these muscles, 

 which is shown in 

 Fig. 56, how, by 

 their successive 

 action from above 



FIG. 56. Muscles of the pharynx, etc. (Sappey). downward, the 



1, 2, 3, 4, 4, superior constrictor : 5, 6. ~, 8, middle constrictor : 9, 10, 11, 12. in- -f n r\f\ ia naaaarl infr 



ferior constrictor ; 13, 13, stylo-pharyngeus ; 14, stylo-hyoid muscle ; 15, 1 



stylo-glossus ; 16, hyo-grlossus : 17, mylo-hyoid muscle; 18, buccinator fV,p rpnnrmo-ii 

 muscle ; 19, tensor palati ; 20, levator palati. 



The muscles 



which form the fleshy portions of the soft palate are likewise important in 

 deglutition. These are the levator palati, the tensor palati, the palato-glossus 

 and the palato-pharyngeus. The azygos uvulae, which forms the fleshy por- 

 tion of the uvula, has no marked or important action in deglutition. 



The mucous membrane of the pharynx, aside from the various glands sit- 

 uated beneath it and in its substance, which have already been described, pre- 

 sents some peculiarities, which are interesting more from an anatomical than 

 a physiological point of view. In the superior portion, which forms a cuboid- 

 al cavity just behind the posterior nares, the membrane is darker and much 

 richer in blood-vessels than in other parts. Its surface is smooth and pro- 



