28 



HUMAN PHYSIOLOGY. 



small spheroidal, granular cells, which border the lumen of the gland, and 

 are known as the chief cells ; the other variety consists of large, oval, well- 

 defined granular cells, much less abundant, and are situated between the 

 basement membrane of the gland and the chief cells. From their position 

 they have been termed parietal cells. During the intervals of digestion 

 the chief cells are pale, and the hyaline substance of which they are com- 

 posed is finely granular. During the stage of active secretion the cells 



FIG. 3. 



Diagram showing the relation of the ultimate twigs of the blood vessels, V and A, and of 

 the absorbent radicles to the glands of the stomach and the different kinds of epithe- 

 lium, viz., above cylindrical cells ; small, pale cells in the lumen, outside which are 

 the dark ovoid cells. From Yeo's Text-Book of PJiysiology. 



become swollen and turbid, and are then said to be rich in pepsin. Toward 

 the end of digestion the granules disappear, the cells become pale and 

 return to their former size. 



During the intervals of digestion, the mucous membrane of the stomach 

 is pale and covered with a layer of mucus. Upon the introduction of food, 

 the blood vessels dilate and become filled with blood, and the mucous 

 membrane becomes, red. At the same time small drops of a fluid, the 



