278 THE ORGANS 



would indicate, the parietal cells have been considered the source 

 of the hydrochloric acid of the stomach. While doubt still exists 

 as to the function of these cells, recent investigations make it probable 

 that they secrete substances which as chlorides are transformed into 

 hydrochloric acid by the action of the carbonic acid of the blood. 

 According to some authorities other cells assist in the production 

 of the stomach acid. The cells of Brunner's glands undergo changes 

 during digestion, which are somewhat similar to those described as 

 occurring in the chief cells of the stomach glands. By some they are 

 beUeved to be concerned in the production of pepsin, by others to 

 play a special role in the secretion of one or more of the intestinal 



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<»,. 





(V 



%\«^'s 



■^i^i 



Fig. i8o. — Section through Glands of Fundus of Human Stomach during Diges- 

 tion. X500. (Bohm and von Davidoff.) a, Lumen; b, stroma; c, chief cell; d, 

 parietal cell. 



ferments. The only function of the surface epithelium and of that 

 of the intestinal crypts which has yet been determined is the secretion 

 of mucus. The cells of Paneth are typical gland cells containing 

 secretion granules and probably produce a specific secretion. (See 

 also page 265.) Whether this secretion is the so-called "inverse 

 ferment" or "invertin^' which changes cane sugar into glucose and 

 levulose or one of the other intestinal ferments has not been deter- 

 mined. It has been known that pancreatic fluid is inactive toward 

 albuminoids unless mixed with intestinal secretions. This is due 

 according to Pavlow to a special ferment " enter okinasey According 

 to some this is a secretion of the epithelium, to others it is elaborated 



