258 



HISTOLOGY 



with that of the oesophagus, but elastic tissue in the muscularis is said to 

 be specially abundant and to "contribute to the tonus of the cardiac mus- 

 culature." The outer longitudinal layer, continuous with the outer layer 

 in the oesophagus and duodenum, is an incomplete layer, being deficient 

 toward the greater curvature. As the body of the stomach bulges out- 

 ward to form this curvature, the longitudinal fibers apparently become 

 separated into scattered bundles. In the pars pylorica, however, there 

 is a continuous longitudinal layer, and some of its fibers, which become 

 intermingled with those of the sphincter pylori, serve to dilate the py- 

 lorus. The innermost layer, composed of oblique fibers, is not represented 



in the oesophagus and duodenum, 

 and is said to be absent from the 

 pars pylorica. The peculiar arrange- 

 ment of its fibers is shown in Fig. 

 250, in which the outer longitudinal 

 layer has been almost entirely re- 

 moved, and windows have been cut 

 through the circular layer; the oblique 

 fibers are seen against the submucosa. 

 They form a longitudinal strand par- 

 allel with the lesser curvature, and 

 they pass from one side of the 

 stomach to the other across the notch 

 between the oesophagus and fundus. 

 These fibers are important in the 

 activity of the gastric canal, but they do not produce the canal as some 

 have supposed. From these longitudinal bundles, fibers curve obliquely 

 toward the greater curvature, where, as transverse fibers they cross to 

 the opposite side. Thus the musculature of the stomach is so arranged 

 that it is very difficult to determine the plane of section in a small piece 

 of gastric mucous membrane, which is usually cut obliquely; but the 

 section shown in Fig. 249, with inner and outer layers cut lengthwise 

 and a middle layer cut across, is consistent with a longitudinal section 

 of the corpus gastri. 



The tunica serosa consists of connective tissue with well-developed elas- 

 tic nets, and a covering of peritoneal epithelium interrupted only along 

 the curvatures, at the mesenteric attachments. It contains the nerves and 

 vessels which supply the stomach. The right and left vagus trunks de- 

 scend beside the oesophagus as the main stems in a plexiform network, 

 and then come together along the lesser curvature. From there they 

 send plexiform branches over both sides of the stomach, and the main 

 stems continue into the small intestine. Sympathetic nerves from the 

 cceliac plexus pass to the pyloric end of the stomach and join the vagus 



FIG 250. A DISSECTION OF THE MUSCULATURE 



OF THE STOMACH. (Spalteholz.) 

 a and e, Longitudinal layer; b and d, circular 



layer; c, oblique layer; Py., pylorus; S. I., 



sulcus intermedius. 



