358 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



all the tubular glands of the stomach. When these cells are clear and 

 large thejr then contain their maximum amount of pepsin. After the 

 secretion of gastric juice has lasted for some time, these cells become 

 contracted and turbid and then contain but a small amount of pepsin. 

 According to certain authorities, pepsin is not directly formed in the cells 

 of these tubular glands, but results from the transformation, by means of 

 hydrochloric acid or sodium chloride, of a mother-substance or zymogen 

 which has been termed pepsinogen. 



Fig. 150.- 



-Pyloric Glands of the Stomach. 

 {Hvidenhain.) 



Fig. 151. — Pyloric Glands — Com- 

 mencing Changes during Diges- 

 tion, after Ebstein. ( Heidcnhain.) 



These statements as to the formation of pepsin are based upon the 

 fact that the secretion withdrawn from the isolated cardiac or pyloric 

 extremity of the stomach contains pepsin in abundance, although the 

 quantity is more marked in the secretion formed by the glands of the 

 fundus. So, also, in the frog, glands simila'r in character to those con- 

 taining chief cells are found in the tubules located in the lower portion 



