CHAPTER XXIV. 



THE ALIMENTABY CANAL. 



BY EDMUND C. WENDT, M.D., 

 Curator of the St. Francis' Hospital, etc., New York City. 



THE human alimentary canal is a tube of great length, ex- 

 tending from the mouth to the anus. There are considerable 

 variations of its calibre in the different regions of the body 

 through which it passes. The two external openings of the 

 digestive tract are continuous with the cutaneous surface of 

 the body. Throughout its entire extent we find several super- 

 imposed layers or membranes, which are from within outward : 

 1, a mucous membrane with its submucosa ; 2, the muscular 

 coat ; and 3, a fibrous layer. In addition to these fundamental 

 strata, we encounter certain special structures, which charac- 

 terize the various parts of the canal. The buccal cavity and 

 pharynx are elsewhere described ; we begin, therefore, with a 

 consideration of 



THE (ESOPHAGUS. 



The walls of this section of the tract are directly continuous 

 with those of the pharynx, and have an average thickness of 

 from three to four millimetres. In the oesophagus, in addition 

 to the four pharyngeal coats, a new layer appears between the 

 epithelial stratum and the submucous tissue. This new struc- 

 ture has received the name of muscularis mucosae. Hence, the 

 different layers of the oesophagus are from within outward : 



1. The mucous membrane. 



2. The muscularis mucosse 



3. A submucous layer. 



4. The muscular coat. 



5. A fibrous envelope. 



The mucous membrane presents comparatively long, coni- 



