70 ALIMENTARY CANAL. 



The mucous coat is marked off from the sub-mucosa by a layer of 

 non-striped muscle (muscularis mucosce) which forms a continuous covering 

 from the stomach downwards, but which is broken up into strands in 

 the oasophagus. 



The muscular coat in the intestine consists of an outer layer with 

 longitudinally-disposed non-striped fibres and an inner one in which the 

 distribution is circular. Between these layers is found the richly- 

 ganglionated nervous plexus of Auerbach. In the stomach the arrange- 

 ment is less regular. In the upper part of the oesophagus striped muscle 

 is substituted (constrictors of the pharynx). 



The sub-mucosa of loose areolar tissue allows free movement to the 

 mucosa when the latter is thrown into folds by the contraction of the 

 gut. Through it blood vessels, nerves and lymphatics (lacteals) run to 

 their points of distribution. In it are found the ganglia of the plexus 

 of Meissner. 



Most of the following sections will in all probability require 

 to be flattened on warm cedar oil. 



(Esophagus. T.S. Dog. (p. 8, s. 17, and iodine green, c. P., 

 m. B.) The mucosa by its large folds practically obliterates 

 the lumen of the tube. Its free surface exhibits stratified 

 squamous epithelium supported by fibrous tissue, which is 

 compact where it meets the epithelium. In this tissue the 

 bands of muscularis mucosse seen in section form a definite 

 outline. In the sub-mucosa clusters of mucous glands occur 

 at frequent intervals and their wide ducts taper to a small 

 aperture where they open through the epithelial covering. The 

 muscular coat is non-striped internally and of the striped 

 variety externally, the section having passed through the 

 region where the transition occurs. Examine (H) the acini 

 lined with secreting epithelium (green) and the muco-mucosse. 



Stomach. C ardio-cesophageal junction. ^.L.S. Cat. (p. 3, inj., 

 s. 22 & 24, c. P., m. B.) (L) Find the point of transition of the 

 epithelium of the oesophagus into the mucosa of the stomach. 



