9 6 



HUMAN PHYSIOLOGY 



from the gastric glands by a soda solution, and can be 

 changed to pepsin by hydrochloric acid. 



(c) Rennin, a coagulating ferment, of unknown composi- 

 tion. It causes the casein coagulation of milk. Its antecedent 

 is rennet-zymogen, which can be extracted from the gastric 

 mucosa by water and can be changed to rennin by the 

 addition of acid. 



The fasting stomach contains no gastric juice ; its mucous 

 membrane is covered with mucus. 



2. Morphological phenomena accom- 

 panying the secretion. The tubular 

 glands of the mucosa may be classi- 

 fied as: 



(a) Glands composed of only one 

 kind of gland-cell. They are found 

 in the pyloric end only and are there- 

 fore called pyloric glands. 



(U] Glands composed of two kinds 

 of cells ; these are found in the fundus 

 fundic glands. 



The pyloric glands contain cylin- 

 drical cells which, in a single layer, 

 form the duct. The fundic glands 

 contain, besides the cylindrical cells 

 (the so-called chief or central cells), 

 also a second kind called the ovoid or 

 oxyntic cells. These ovoid cells lie 

 isolated between the chief cells and 

 the membrana propria and do not 

 form a continuous layer. The ovoid 

 cells are surrounded by secretory capil- 

 lary loops in a basket-like form, which ovoid cells is darker and 



are connected with the lumen of the gj^ (.f^STce* 



gland. (b} of the fundic glands. 



Both the fundic and pyloric glands form pepsin and rennin, 

 hence the cylindrical cells (chief cells of the fundic glands) must 

 be regarded as secreting pepsin and rennin. 



FIG. 4. FUNDIC GLANDS. 



(After Heidenhain. ) 

 The protoplasm of the 

 chief cells is clear, that of the 



