294 CHEMICAL MECHANISMS OF SECRETION 



to the secreting cells of the fundus, where it acts as a chemical 

 stimulant, and calls forth secretion. 



Edkins has studied the effects of intravenous injection of 

 extracts made from different parts of the gastric mucosa. He 

 placed a certain amount of saline in the stomach, and then deter- 

 mined the amount of acid formed in the stomach, after the injection 

 of each extract to be tested into a vein, by titrating this saline for 

 total acidity. 



The results obtained were as follows : 



"If an extract in 5 per cent, dextrin of the fundus mucous 

 membrane be injected into the jugular vein, there is no evidence 

 of secretion of gastric juice. If the extract be made with the 

 pyloric mucous membrane there is evidence of a small quantity 

 of secretion. With dextrin by itself there is no secretion. 



" Extracts of fundus mucous membrane in dextrose or maltose 

 give no secretion ; extracts of pyloric mucous membrane give marked 

 secretion ; dextrose or maltose alone brings about no secretion. 



" If extracts be made with commercial peptone, it is found 

 that no secretion occurs with the fundus mucous membrane, a 

 marked secretion with the pyloric mucous membrane; the peptone 

 alone gives a slight secretion. 



" If the extracts be made by boiling the mucous membrane 

 in the different media, the effect is just the same that is to say, 

 the active principle, which may be called ' gastrin,' is not destroyed 

 by boiling. 



" Finally, it may be pointed out that such absorption as occurs 

 in the stomach apparently takes place at the pyloric end. In 

 the pig's stomach, in which the cardiac region differs from the 

 ordinary type in only having simple glands as in the pyloric, 

 extracts of the cardiac region in general have the same efficiency 

 in promoting secretion as do pyloric." 



The media most powerful in calling forth secretion in these 

 experiments are hence those containing the products of advanced 

 salivary digestion, or of peptic digestion viz., glucose, maltose, 

 and commercial peptone and the region from which active pre- 

 parations can be prepared being the pyloric mucous membrane, 

 which also is the region in which any slight absorption in the 

 stomach occurs, the indication of the experiments is that the 

 precursor of the active gastrin is formed in the pyloric mucosa, 

 and is activated by the absorption of these digestive products, 



