178 DIGESTION 



relaxed, presents a concave surface looking toward the mouth, a free 

 arched border, and a conical process hanging from the centre, called 

 the uvula. On either side of the soft palate, are two curved pillars, 

 or arches. , 



The anterior pillars of the palate are formed by the palato-glossus 

 muscle on either side and run obliquely downward and forward, their 

 membrane becoming continuous with the mucous membrane covering 

 the base of the tongue. The posterior pillars are more closely ap- 

 proximated to each other than the anterior. They run obliquely down- 

 ward and backward, their mucous membrane becoming continuous with 

 the membrane covering the sides of the pharynx. Between the lower 

 portion of the anterior and posterior pillars, are the tonsils ; and in the 

 substance of and beneath the mucous membrane of the palate and 

 pharynx, are small glands, which have already been described. 



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; 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 posterior nares and 

 the Eustachian tubes. Below, are the openings of the oesophagus and 

 the larynx. 



The muscles of the pharynx are the superior constrictor, the stylo- 

 pharyngeus, the middle constrictor and the inferior constrictor; and 

 it is easy to see, from the situation of these muscles, how, by their 

 successive action from above downward, the food is passed into the 

 oesophagus. 



The muscles forming the fleshy portions of the soft palate are like- 

 wise 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 portion of the uvula, has no important action in 

 deglutition. 



The mucous membrane of the pharynx, aside from the various 

 glands situated beneath it and in its substance, presents certain peculiar- 

 ities. In the superior portion, which forms a cuboidal 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 is provided with 

 ciliated epithelium like that which covers the membrane of the posterior 

 nares. Laterally, below the level of the opening of the Eustachian 

 tubes, and posteriorly, at the point where it becomes vertical, the mucous 

 membrane abruptly changes its character. The epithelial covering is 

 here composed of stratified cells similar to those which cover the mucous 

 membrane of the oesophagus; and the membrane is paler and less 



