DEGLUTITION. 



The openings into the pharynx above are the posterior nares and orifices of the Eusta- 

 chian 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 superior constrictors form the muscular wall of the upper part of the pharynx. 

 Their origin extends from the lower third of the margin of the internal pterygoid plate of 

 the sphenoid bone to the alveolar process of the last molar tooth, the intermediate line of 

 attachment being to tendons and ligaments. The fibres then pass backward and meet in 

 the median raphe, which is attached by aponeurotic fibres to a ridge on the basilar process 

 of the occipital bone, called the pharyngeal spine. 



The stylo-pharyngeus muscle has a rounded portion above, by which it arises from the 

 inner surface of the base of the styloid process of the temporal bone. It passes between 

 the superior and middle constrictors of the pharynx, becomes thin, and spreading out, its 

 fibres mingle in part with the fibres of the constrictors and the palato-pharyngeus, and a 

 few pass to be inserted into the upper border of the thyroid cartilage. 



Tho middle constrictor is a flattened muscle, arising from the cornua of the hyoid bone 

 and the stylo-hyoid ligament, its fibres passing backward, spreading into a fan-shape, and 

 meeting in the median raphe. 



The inferior constrictor is the most powerful of the muscles of the pharynx. It arises 

 by thick, fleshy masses from the sides of the thyroid and cricoid cartilages of the larynx. 

 The inferior fibres curve backward, and the superior fibres, backward and upward, to 

 meet in the median raphe. 



The muscles which form the fleshy portions of the soft palate are likewise important 

 in deglutition. 



The levator palati, a long muscle of considerable thickness, arises from the apex of the 

 petrous portion of the temporal bone and the adjacent cartilaginous portion of the Eusta- 

 clrian tube ; and, spreading out in the posterior portion of the soft palate, as its name 

 implies, it raises the velum. 



The tensor palati, sometimes called the circumflexus, is a broad, thin muscle, consist- 

 ing of a vertical portion, which is fleshy, and a horizontal portion, which is tendinous. 

 The fleshy fibres arise from the scaphoid fossa of the sphenoid bone, pass downward, be- 

 come tendinous, and wind around the hamular process ; after which the muscle spreads 

 out into a thin aponeurosis, which passes to the median line on the anterior portion of 

 the soft palate. Its action is to render the palate tense. 



The palato-glossus forms the anterior pillar of the soft palate. It arises from the side 

 of the palate near the uvula and passes to be inserted into the side and dorsum of the 

 tongue. The action of this muscle is to constrict the isthmus of the fauces, by drawing 

 down the soft palate and elevating the base of the tongue. 



The palato-pharyngeus forms the posterior pillar of the soft palate. It arises from the 

 soft palate by two fasciculi, and joins with the fibres of the stylo-pharyngeus, to be in- 

 serted into the posterior border of the thyroid cartilage. Its action is to approximate the 

 posterior pillars of the palate and depress the velum. 



The azygos uvulse is the small muscle, consisting of two fasciculi, one on either side, 

 which forms the fleshy portion of the uvula. It has no very marked or important action 

 in deglutition. 



The mucous membrane of the pharynx, aside from the various glands situated 1 

 it and in its substance, which have already been described, presents some peculiars 

 which are interesting more from an anatomical than a physiological point of view. 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 provided with ciliated, columnar epithelium, like that which covers the mem- 



