THE ALIMENTARY CANAL. 113 



THE (ESOPHAGUS. 



The oesophagus contains four characteristic coats the mucosa, 

 the sub-mucosa, the muscular coat, and the fibrous coat. 



The mucosa consists of stratified squamous epithelium resting 

 upon a tunica propria, or connective tissue stroma, beneath which 

 is a thin layer of involuntary muscle, the muscularis mucosw. The 

 tunica propria is composed of fibrous connective tissue and contains 

 blood-vessels and lymphatics. 



The sub-mucosa lies beneath the muscularis mucosas, and con- 

 sists of loose connective tissue, containing blood-vessels, nerves, and 

 glands of the racemose variety. 



The muscular coat, in the upper end of the oesophagus, is com- 

 posed of striated fibres ; in the lower end, of smooth muscle ; while 

 the middle portion contains both smooth and striated fibres. 



The fibrous coat envelops the muscular coat, contains elastic tis- 

 sue, and forms an attachment to the adjacent areolar tissue. 



Laboratory exercise No. 33. Tfie (Esophagus. Harden in corrosive 

 sublimate, embed in celloidin, and stain with carmine, method No. 3. 

 Examine with L. P. Demonstrate the epithelial layer, stroma and mus- 

 cularis mucosse of the mucosa. Search for blood-vessels, nerves, and 

 glands in the sub-mucosa. Examine the muscular coat, and determine 

 from your preparation the part of the ossophagus from which the tissue 

 was obtained. Note the structure of the fibrous coat. Is there an endo- 

 thelial layer? Do you find any investing areolar tissue? 



THE STOMACH. 



Tlie stomach has the usual coats mucosa, sub-mucosa, muscular 

 coat, and serous coat. 



The mucosa is lined superficially with a single layer of columnar 

 epithelium, the squamous epithelium of the oesophagus having ended 

 abruptly at the cardiac orifice. Besides the epithelial layer the 

 mucosa contains the basement membrane, the stroma, the muscularis 

 mucosce, and the gastric glands. The gastric glands are of two kinds 

 peptic and pyloric. The peptic glands are of the simple tubular 

 variety, consisting of basement membrane, secreting cells, and duct. 

 The mouth of the duct is marked by a slight depression upon the 

 surface of the mucous membrane. These glands are found on the 

 cardiac and middle thirds of the stomach, and are provided with 



