STRUCTURE OF STOMACH. 



319 



iens shows it to be covered with minute shallow pits. Into 

 these open the mouths of minute tubes, the gastric glands, 

 which are closely packed side by side in the mucous 

 membrane; there being between them only a small amount 

 of connective tissue, a close network of lymph-channels, 

 and capillary blood-vessels. The whole surface of the 

 mucous membrane is lined by a single layer of columnar 

 epithelium cells (Fig. 97). These dip down and line the 

 tubular glands, being in some (especially those about the 

 pyloric end of the stomach) but little modified in appear- 

 ance (c, Fig. 97). In others the epithelial cells become 

 shorter and cuboidal, and 

 have beneath them (a and Z>, 

 Fig. 97) a second incomplete 

 layer of much larger oval 

 cells, d. The glands of this 

 second kind are the most 

 numerous, and have been 

 called peptic glands from 

 the idea that they alone 

 formed pepsin, the essential 

 digestive ingredient of the 

 gastric juice; this is how- 

 ever by no means certain, peptic ceils. 

 The peptic glands frequently branch at their deeper 

 ends. 



The Pylorus. If the stomach be opened it is seen that 

 the mucous membrane projects in a fold around the pyloric 

 orifice and narrows it. This is due to a thick ring of the 

 circular muscular layer there developed, and forming a 

 sphincter muscle around the orifice, which in life, by its 

 contraction, keeps the passage to the small intestine closed 

 except when portions of food are to be passed on from 

 the stomach to succeeding divisions of the alimentary 

 canal. 



Note. The cardiac end of the stomach lying immediately 

 beneath the diaphragm, which has the heart on its upper 

 side, over-distension of the stomach, due to indigestion or 

 flatulence, may impede the action of the thoracic organs, and 



FIG. 97. A thin section through the 

 gastric mucous membrane, perpendi- 

 cular to its surface, magnified about 

 25 diameters, a, a simple peptic gland 



6, a c mpound peptic gland: c, a mu- 

 cous gland ; d, oval, chief, or so-called 



