65 
appear to be present in the intestine of the plaice. Nor is 
the peculiar “stratum compactum” of the submucosa 
which Oppel has described in some other fishes certainly 
present. 
The Stomach (fig. 21) is sharply distinguished from 
cesophagus and duodenum by the strongly developed 
transverse musculature at its proximal and distal ends. 
The transverse muscle layer is less strongly and the longi- 
tudinal layer more strongly developed than in the 
esophagus. At its pyloric end the transverse muscle 
layer becomes much thicker and forms the prominent 
sphincter pylori, a valve which projects into the cavity 
of the duodenum. There is also a very marked differentia- 
tion of the mucosa. In the esophagus this consists of a 
simple columnar epithelium with goblet cells. In the 
stomach the goblet cells disappear and the epithelium is 
evaginated to form a closely-set series of gastric glands 
over the whole internal surface. Each gland is a tubule, 
the internal portion of which is straight and the deeper 
portion convoluted. The straight or condueting portion 
has a wall consisting of columnar cells with a cement 
substance between them, and the lumen is relatively wide. 
The deeper or secreting portion has walls made up of large 
cubical clear cells, whilst the lumen is narrow. The sub- 
mucosa consists of loose areolar tissue containing blood 
vessels. The stomach lies along the dorsal wall of the 
body cavity, and the pylorus is situated at the posterior 
end of the kidney. i: 
The Duodenum lies along the posterior wall of the 
body cavity towards the eyeless side of the body. Its 
proximal end is slightly folded over the distal end of the 
stomach. Its wall (and that of the succeeding regions of 
the alimentary canal) is thin and consists of an outer longi- 
tudinal and an inner transverse layer of unstriated muscle 
H 
