920 THE EXTERNAL SECRETIONS 



tion next to the lumen of the duct. These cells line the entire secretory portion of 

 these glands and are known as central or chief cells. Wedged in between these 

 and the basement membrane are a number of isolated cells which present a 

 spheroidal or ovoid shape, and are connected with the main duct by a network 

 of minute channels situated in between the chief cells. Nearer the duct, these cells 

 are more abundant and occupy a position in between the chief cells and close to 

 the lumen (Bensley). These cells are known as the parietal or oxyntic (acid) cells. 

 (c) The glands of the pyloric end, which are scattered throughout the pyloric 

 canal, are much longer than those of the fundus and are made up wholly of chief 

 cells. The latter bear a close resemblance to those composing the fundic glands, 

 but are not quite so granular. Directly at the pylorus they increase in size, and 

 become more convoluted and more deeply seated. They are thus gradually 

 transformed into the glands of Brunner of the submucous layer of the duodenum. 



Histological Changes in the Gastric Glands on Secretion. — Accord- 

 ing to Heidenhain, the chief cells of the inactive glands are large and 

 clear, save for a certain amount of granular material which is collected 

 very largely near the duct. During secretion, these granules are dis- 

 charged into the duct, leaving the outer zones of the cells perfectly 

 clear. ^ The parietal cells undergo a similar diminution in their size, 

 but do not exhibit so distinct a clearing of their cytoplasm. Thus, we 

 are again confronted by the fact that these cells do not merely form a 

 pumping mechanism for water, but actively concentrate the original 

 liquid by preformed material. 



The Origin of the Active Principles of Gastric Juice. — Heidenhain ^ 

 conceived the idea of isolating a certain portion of the stomach and 

 giving it an artificial fistulous opening to the outside through which 

 gastric juice could be obtained separately from its different segments. 

 This operative procedure has been improved upon by Pawlow^ in 

 such a way that these gastric pockets need not be deprived of their 

 normal blood and nerve supply. Upon analysis of these different 

 samples of gastric juice it was found that the secretion from the pyloric 

 end is free from hydrochloric acid, but not from pepsin, while that 

 from a cul-de-sac of the fundus is strongly acid in reaction and contains 

 much pepsin. Inasmuch as the pyloric glands are made up of chief 

 cells, while the fundic glands also embrace border cells, it was then 

 concluded that the pepsin is furnished by the chief cells, and the 

 hydrochloric acid by the parietal cells. 



In support of this hypothesis it has been shown that the esophagus 

 of the frog is beset with glands which are made up of chief cells and 

 secrete only pepsin, while the glands of the fundus of the stomach are 

 composed of ovoidal cells which produce large quantities of acid but 

 little pepsin. Further light is thrown upon this topic by the fact 

 that the secretion taken from the pyloric cul-de-sac, does not digest 

 protein material nor curdle milk unless it is acidified by the addition of 

 dilute hydrochloric acid. Thus, while these glands secrete pepsin, 

 this agent remains impotent as long as it is permitted to remain in an 



1 Langley, Jour, of Physiol, iii, 1880, 269. 



2 Hermann's Handb. der Physiol., 1883. 



3 Die Arbeit der Verdauungsdriisen, Wiesbaden, 1898. 



