XXII.] 



(ESOPHAGUS. 



255 



processes fibres of Tomes may be seen partially withdrawn from 

 the dentiiial tubules in which they lay. 



(ESOPHAGUS. 



The (Esop-agus consists from within outwards of 



(i.) Mucous coat, composed of stratified squamous epithelium, 

 into which project small simple papillae from the corium or con- 

 nective-tissue basis of the membrane. At the. outer part of the 

 eoriimi is a narrow layer of smooth muscular fibres muscularis 

 mucosse arranged for the most part longitudinally. 



(2.) Submucous coat, consisting of connective tissue and the 

 larger blood-vessels and some nerves. In those animals (e.</., dog) 

 in which glands occur, the acini of the 

 glands lie in the submucous coat, so that 

 their duets have to perforate the muscu- 

 laris nmcosne and traverse the mucous 

 membrane before they open on the surface 

 of the epithelium. 



(3.) Muscular coat. This will vary 

 with the animal used. In man this coat 

 in the upper third of the oesophagus is 

 composed of striated muscular fibre, the 

 lower two-thirds of smooth muscle. The 

 outer layer of fibres runs longitudinally, 

 the inner circularly. 



(4.) Fibrous coat, composed of fibrous 

 tissue. 



4. The (Esophagus. Cut out a piece 

 of the oesophagus of a dog or cat 2 cm. 

 in length and harden it in equal parts 



of chromic acid (i per cent.) and spirit, or FIG. 248. T.S. Small Part of 

 Miiller's fluid (fourteen days), or mercuric 

 chloride, and then in alcohol. Make 

 transverse sections ; stain one in picro- 

 carmine and mount it in Warrant's solu- 

 tion, and another in logwood and mount 

 it in balsam. Perhaps even more instructive sections are obtained 

 from a small animal, such as a rat, where the whole oesophagus (with 

 trachea) can be stained "in bulk" in borax-carmine. Cut sections 

 of both tubes to show their structure and relations. 



(a.) (L and H) The circular tube has several coats, the inner- 

 most one being thrown into folds. The mucous membrane covered 

 by stratified sipiamous epithelium, under this the connective tissue 



(Esophagus of Dog. E. Epi- 

 thelium ; M. M. Muscularis 

 mucosac; G. Glands; C. Cir- 

 cular, and L. External or 

 longitudinal muscular coat; 

 F. Fibrous layer. Miiller's 

 fluid, picro-carmine. 



