338 



THE HUMAN BODY. 



lion of the inner surface of the stomach with a hand lens 

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

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

 are closely packed side by side in the mucous membrane; 

 something like the cells of a honeycomb, except that each is 

 open at one end. Between them lie a small amount of con- 

 nective tissue, a close network *f lymph-channels, and capil- 

 lary blood-vessels. The connective tissue is of a peculiar 

 variety closely packed with lymph-cells and will be more mi- 

 nutely described later (Chap. XXIII). The whole surface of 

 the mucous membrane is lined by a single layer of columnar 

 mucus-making epithelium cells (Fig. 113). These dip down 

 and line the necks of the tubular 

 glands. The deeper portions of the 

 glands are lined by a layer of 

 shorter and somewhat cuboidal cells, 

 the central or chief cells. In speci- 

 mens taken from a healthy animal 

 killed during digestion these cells are 

 large and do not stain deeply with 

 carmine. Similar specimens taken 

 from an animal an hour or two 



FIG. 113. A thin section 



through the gastric mucous alter a good meal has been swallowed 



membrane, perpendicular to its , .? 7 . ,. ,, , , , 



surface, magnified about 25 di- SllOW tllC CniCJ Cells Shrunken and 

 anieters. a, a simple gastric , -i i rni ,1 



gland ; 6, a compound gastric staining more deeply. They, thus, 



store up during rest a material which 

 they get rid f when the gastric juice 

 is being secreted. This material 5s, 

 in part, pepsinogen, which during activity of the gland is 

 changed, giving rise among other things to pepsin, the chief 

 enzyme of gastric juice. The deeply staining protoplasmic 

 portion of the cell which is left behind, forms and stores more 

 pepsinogen during the next period during which the stomach 

 is not digesting. In the pyloric end of the stomach only the 

 chief jlells line the glands, but elsewhere there is found out- 

 side them, in most of the glands, an incomplete layer of larger 

 tvtl cells (d, Fig. 113). These are sometimes called the 

 txinitic cells, from the belief that they are especially con- 

 cerned in secreting the acid of the gastric juice. The 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 



vc 



; ' retif rm 



