37H 



t. to :i lissnrc in the superior border of the liver, ami is enveloped by the 

 peritoueum. 



Iff' riur. Internally, the canal whoso course and relations we have jiift 

 studied prc.-cnts nothing of interest; and it only re.quins t" be remarked, 

 that its walls are always shrunken and in contact when food is not passing 

 'n them. 



STKUCTURB. The oesophagus has two tunics : a mucous and a muscular. 



The mucous membrane is continuous with that of the pharynx and the 

 stomach; it is white, and shows numerous longitudinal folds which allow 

 the canal to dilate. It adheres but loosely to the muscular coat, on which 

 it can glide with the greatest facility. It has a thick, resisting, stratilied, 

 tessclated epithelium, an uustriped muscular layer, and some racemose 

 glands. 



Fig. 179. 





PECTORAL CAVITY AND Sir.lH A-TIM'M, SHOWING THE COURSE OF THE TRACHE.t; 

 AM) 'I.Sol-IIAGCS. 



(A third or inliliUe coat is sometimes mentioned by anatoini.-ts ; it is 

 composed of the tissue connecting the latter tunic with the one to IK- next 

 described.) 



The muscttlar coat commences at the posterior part of the pharynx by 

 tin ;uyt( -no-pharyngei muscles, and by two small superficial bands which 

 an- detached from the posterior portion of tlie crico-pharyngci uui 

 This tunic is formed of superficial longitudinal fibres, often assembled in 

 uli ; and of a deeper series of spiral or circular fibres, \\hich, towards 

 til- inferior extremity of the canal, intercross in an almost in 

 manner. This muscular layer in the cervical, and fora great part of the 

 thomeic j>. >rtion of the oesophagus, has the rod colour of voluntary mu 

 but it Ix/ronies white, like the involuntary fibres, after the conduit t 



mediastinum, and acquires considerable thickness and marked rigidity. 

 It is to b> -hat this arrangement of the muscular tunic is especially 



