214 GASTRIC DIGESTION. 



the aid of a simple lens, as many of them are quite small. The diameter of 

 the pits is very variable, but the average is about ^-g- of an inch (O125 mm.). 

 This appearance is not distinct toward the pylorus ; the membrane here pre- 

 senting irregular, conical projections and well marked villi resembling, those 

 found in the small intestine. The surface of the mucous membrane is cov- 

 ered with columnar or prismoidal epithelium, the cells being tolerably regular 

 in shape, each with a clear nucleus and a distinct nucleolus. According to 

 Landois, these cells, which he calls " mucus-secreting gob- 

 let-cells," have a clear portion occupying their outer half, 

 which is open and discharges a viscid secretion. 



The thickness of the mucous membrane of the stom- 

 ach varies in different parts. Usually it is thinnest near 

 the oesophagus and thickest near the pylorus. Its thin- 

 nest portion measures -fa to ^ of an inch (0-34 to 0-5 

 no. m.-Gob*t-eeUs mm -) 5 its thickest portion, fa to fa of an inch (1-6 to 

 stomach 2'1 mm.), and the intermediate portion, about fa of an 



inch (1 mm.). 



Glands of the Stomach. Extending from the bottoms of the pits in the 

 mucous membrane of the stomach to the submucous connective tissue, are 

 large numbers of glands. These generally are arranged in tolerably dis- 

 tinct groups, surrounded by fibrous tissue, each group belonging to one of 

 the polygonal depressions. The tissue which connects the tubes is dense but 

 not abundant. There are marked differences in the anatomy of the glands 

 in different parts of the stomach, which are supposed to correspond with 

 differences in the uses of various parts of the mucous membrane. There are, 

 indeed, two distinct varieties of glands; the peptic glands, which secrete 

 pepsine, or an organic substance that is readily changed into pepsine, and the 

 acid-glands, which are supposed to secrete free hydrochloric acid. The pep- 

 tic glands are most abundant in the pyloric portion of the stomach and 

 around the cardiac opening. The so-called acid-glands are found through- 

 out the mucous membrane, especially in the greater pouch. The secretion 

 in the pyloric portion of the stomach is not acid at any time, while the se- 

 cretion in the greater pouch, during digestion, is always strongly acid. The 

 difference in the action of these two kinds of glands is supposed to depend 

 upon differences in the secreting cells. 



The pyloric glands are lined by cells which may be called peptic cells (the 

 chief-cells of German writers), conoidal or cuboidal in form, and relatively 

 clear, especially during the intervals of digestion. Similar cells are found, in 

 connection with the so-called acid-cells (parietal cells) in the secreting por- 

 tion of the glands of the greater pouch. 



The acid-glands are found throughout the stomach, except near the pylo- 

 rus. The secreting portion of these glands contains peptic cells, but near 

 the tubular membrane are rounded cells, larger than the peptic cells, darker 

 and more granular, which are the acid, or parietal cells. These are strongly 

 stained when treated with osmic acid (Nussbaum). It is probable that the 

 so-called acid-glands secrete pepsine as well as an acid, while the pyloric 



