212 



GASTRIC DIGESTION. 



lar fibre-cells, are very pale, with faint outlines, fusiform or spindle-shaped, 

 and contain each an oval, longitudinal nucleus. They are closely adher- 

 ent 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 -fa of 

 an inch (1 mm.). In the pylorus its thickness is -fa to -fa of an inch (1-6 to 

 2-1 mm.), and in the fundus, -fa to -fa of an inch (O5 to - 7 mm.). 



The muscular fibres exist in the stomach in two principal layers ; an ex- 

 ternal longitudinal layer and an internal circular layer, with a third layer of 

 oblique fibres extending over the great pouch only, which is internal to the 

 circular layer. The longitudinal fibres are continued from the oesophagus 

 and are most marked over the lesser curvature. They are not continued 

 very distinctly over the rest of the stomach. The circular and oblique 

 fibres are best seen with the organ everted and the mucous membrane care- 

 fully removed. The circular layer is not very distinct to the left of the car- 

 diac opening, over the great pouch. Toward the pylorus, the layers of fibres 

 are thicker, and at the opening into the duodenum, they form a powerful 

 muscular ring, which is sometimes called the sphincter of the pylorus, or the 

 pyloric muscle. At this point they project considerably into the interior of 

 the organ and cease abruptly at the opening into the duodenum, so as to form 

 a sort of valve, presenting, when contracted, a flat surface looking toward the 



10 



FIG. 57. 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 ; 11, circular fibres seen through the thin layer of longitudinal fibres. 



intestine. The oblique layer takes the place, in great part, of the circular 

 fibres, over the great pouch. It extends obliquely over the fundus from left 



