1 86 GASTRIC DIGESTION 



ordinary fibrous tissue with a considerable number of elastic fibres. It 

 is closely adherent to the subjacent muscular coat and is not very 

 abundantly supplied with bloodvessels and nerves. Lymphatics have 

 been demonstrated only in the subserous structure. The surface of 

 the peritoneum is everywhere covered with regularly-polygonal cells of 

 endothelium, closely adherent to each other and presenting a smooth 

 surface moistened with a small quantity of liquid. 



Muscular Coat. Throughout the alimentary canal, from the cardiac 

 opening of the stomach to the anus, the muscular fibres forming the 

 middle coat are of the non-striated variety. These fibres are pale, with 



Fig. 36. Longitudinal fibres of the stomach (Sappey). 



I, lesser curvature; 2, 2, greater curvature; 3, greater pouch; 4, lesser pouch; 5, 6, 6, lower end 

 of the oesophagus ; 7, 7, pylorus ; 8, 8, longitudinal fibres at the lesser curvature ; 9, fibres extending 

 over the greater curvature ; 10, 10, a very thin layer of longitudinal fibres over the anterior surface of 

 the stomach; n, circular fibres seen through the thin layer of longitudinal fibres. 



faint outlines, fusiform or spindle-shaped, containing each an oval longi- 

 tudinal nucleus. They are closely adherent by their sides and are so 

 arranged as to dovetail into each other, forming sheets of greater or less 

 thickness depending upon the number of their layers. The muscular 

 coat of the stomach varies in thickness in different animals. In the 

 human subject it is thickest in the region of the pylorus and is thinnest 

 at the fundus. Its average thickness is about ^ of an inch (i milli- 

 meter). In the pylorus its thickness is ^g- to ^ of an inch (1.6 to 2.1 

 millimeters), and in the fundus, ^ to -% of an inch (0.5 to 0.7 millimeter). 

 The muscular fibres are in two principal layers ; an external longi- 

 tudinal layer and an internal circular layer, with a third layer of oblique 



