DEGLUTITION. 



215 



and, finally, a peristaltic action of the muscular walls of the oesophagus, extending from 

 its opening at the pharynx to the stomach. 



Physiological Anatomy of the Parts concerned in Deglutition. The parts concerned 

 in this function are the tongue, the muscular walls of the pharynx, and the oesophagus. 

 In the passage of food and drink through the pharynx, it is necessary to completely pro- 

 tect from the entrance of foreign matters a number of openings which are exclusively for 

 the passage of air. These are above, the posterior nares and the Eustachian tubes, and 

 below, the opening of the larynx. The mechanism by which these passages are closed 

 during the acts of deglutition is one of the most interesting subjects connected with this 

 function and has long engaged the attention of physiologists. 



The tongue a muscular organ capable of a great variety of movements, and en- 

 dowed, as we have seen, with highly important functions connected with mastication 

 is the chief agent in the first processes of deglutition. Its physiological anatomy has 

 already been considered. 



FIG. 52. Cavities of the mouth and pharynx, etc. (Sappey.) 



Section in the median line of the face and the superior portion of the neck, designed to show the mouth in its rela- 

 tions to the nasal fossae, the pharynx, and the larynx : 1, sphenoidal sinuses ; 2, internal orifice of the Eustachian 

 tube ; 3, palatine arch ; 4, velum pendulum palati ; 5, anterior pillar of the soft palate ; 6. posterior pillar of the 

 soft palate ; 7, tonsil ; 8. lingual portion of the cavity of the pharynx ; 9, epiglottis ; 10, section of the hyoid 

 bone ; 11, laryngeal portion of the cavity of the pharynx ; 12, cavity of the larynx. 



The pharynx, in which the most vigorous and complex of the movements of degluti- 

 tion take place, is an irregular, funnel-shaped cavity, its longest diameter being trans- 

 verse and opposite the cornua of the hyoid bone, with its smallest portion at the opening 

 into the oesophagus. Its length is about four and a half inches. It is connected superiorly 

 and posteriorly with the basilar process of the occipital bone and the upper cervical verte- 



