STOMACH 253 



oesophagus, and the transition is abrupt. The outer strata of the cesopha- 

 geal epithelium may form an overhanging wall (Fig. 243), or the number of 

 layers may have become reduced so that such a wall is absent. Sometimes 

 an island of stratified epithelium occurs just beyond the line of transition. 

 The gastric epithelium forms three types of glands, known as cardiac, 

 gastric, and pyloric glands respectively, none of which extend into the 

 submucosa. 



The cardiac glands are like the superficial glands at the lower end of the 

 oesophagus, of which they may be regarded as a continuation. They ex- 

 tend only from 5 to 40 mm. into the stomach, and in the narrow zone which 

 they occupy, they present a gradual transition to the gastric glands. 

 Their branches, instead of continuing divergent, become groups of per- 

 pendicular tubes descending from epithelial pits; and deeply staining 

 eosinophilic cells and the granular chief cells become included in their 

 epithelium. 



The cells characteristic of the cardiac glands contain a mucus which 

 does not respond readily to mucin stains. Like the superficial glands of 

 the oesophagus, the cardiac glands develop early, and they are found widely 

 distributed among mammals. 



The gastric glands (sometimes inappropriately called fundus glands) 

 occur over the entire surface of the stomach, except near the cardia and py- 

 lorus. Each gastric gland is divided into an outer portion, or gastric pit 

 (foveola gastrica] , and a group of slender cylindrical tubules which empty 

 into the bottom of the pit. During development, as the lining of the stom- 

 ach expands greatly, the number of pits increases. Toldt estimated that 

 there were 129,912 in the stomach at three months; 268,770 at birth and 

 2,828,560 at ten years. The increase is accomplished by division of the 

 pits from below upward. In spite of the fact that many new branches 

 develop, the average number of tubules emptying into each pit becomes 

 reduced as the pits become subdivided; and the average of seven per pit 

 observed at birth becomes three in the adult (Toldt, Sitz.-ber. Akad. d. 

 Wiss. Wien, 1881, vol. 82, pp. 57-128). 



The pits are often described as if they were epithelial depressions sepa- 

 rate from the glands, since the same sort of epithelium which lines them is 

 found on the free surface. Developmentally, however, they are to be re- 

 garded as parts of the glands, comparable with ducts. The epithelial cells 

 of the pits (Fig. 245) consist of a basal protoplasmic portion containing elon- 

 gated, round, or sometimes flattened nuclei, and an outer portion contain- 

 ing the centrosome and secretion. The mass of mucus may cause the thin 

 top plate to bulge, and in preserved tissue to rupture, but this may be due 

 to reagents. The mucus first appears in granular form. 



The gastric tubules are straight or somewhat tortuous slender struc- 

 tures, with narrow lumens. The portion which joins the pit constitutes 



