THE (ESOPHAGUS. 29 



— The commencement of the cavity of the pharynx, from 

 the base of the cranium, and its position behind the posterior 

 opening of the cavities of the nose, mouth, and glottis, are 

 well seen in fig. 134, page 28. Its termination below, and the 

 commencement of the oesophagus are seen at i. — 



The pharynx has been above described* as composed of a 

 varied stratum of muscular fibres, lined by a membrane which 

 is continued from the internal surface of the nose and mouth. 

 From the pharynx the oesophagus passes downwards between 

 the trachea, and the vertebrae. After the bifurcation of the 

 trachea, it proceeds in contact with the spine, between the 

 lamina of the mediastinum to the diaphragm, which it passes 

 through, and then terminates in the stomach. 



The oesophagus is a flexible tube, which, when distended, is 

 nearly cylindrical. It consists of a muscular coat externally, 

 and an internal tunic evidently continued from that of the 

 pharynx. These coats are connected by a cellular substance 

 called the Nervous Coat,f which is remarkably loose, and 

 allows them to move considerably upon each other. The 

 muscular coat, which is very distinguishable from that of the 

 pharynx, consists of two substantial strata of fibres; the 

 exterior of which is nearly longitudinal in its direction, and the 

 interior circular or transverse. 



— The longitudinal fibres appear to arise in part from the 

 posterior face of the cricoid cartilage, between the posterior 

 crico-arytenoid muscles, and part from the lower end of the 

 pharynx ; They are disposed regularly around the oesophagus, 

 and below are manifestly continuous with the longitudinal 

 muscular fibres of the stomach. The first ring of the circular 

 fibres, also seems to arise from the cricoid cartilage, and has 

 been described as the crico-oesophageal muscle. There is no 

 sphincter, at the junction of the oesophagus with the stomach 

 as has been asserted by some anatomists. 



* See Vol. i. p. 490. 



f The nervous coat, is as before observed nothing but a structure of submucous 

 cellular tissue, which connects the mucous membrane, as the subcutaneous 

 cellular tissue does the skin to the pans subjacent, and through which the nerves 

 and blood-vessels ramify, before they spread minutely in the mucous mem- 

 brane. — F. 



3* 



