CHAPTER XVII 



THE INTERNAL SECRETIONS OF THE ALIMENTARY 

 MUCOUS MEMBRANE AND OF THE PANCREAS 



SECRETINES 



BAYLISS and Starling discovered in 1902 that an extract of the duodenal 

 mucous membrane, or even of its epithelium alone, if injected into the 

 circulating blood, produces a rapid secretion of pancreatic juice (fig. 87). 

 In Bayliss and Starling's experiments the active substance was obtained by 

 boiling the mucous membrane with dilute hydrochloric acid and afterwards 



a 



b 

 c 



d 



FIG. 87. Effect on blood-pressure and secretion of pancreatic juice of injecting into a vein 

 extract of mucous membrane of duodenum, made by boiling with dilute hydrochloric 

 acid and subsequently neutralising. (Bayliss and Starling.) 



a, blood-pressure : notice the sharp fall followed by return to normal ; b, drops of pancreatic juice ; 

 c, signal ; d, time in seconds. 



neutralising and filtering : the autacoid (hormone) is contained in the filtrate. 

 They observed little or no activity from extracts of membrane which 

 had not been treated with acid, and concluded that the active substance 

 (secretine) is present in the cells in an inactive form (pro-seer 'etine), and be- 

 comes activated (converted into secretine) by the action of the acid. It had 

 been previously found that rinsing the duodenum with dilute mineral acid 1 



1 According to Babkin and Ishikawa, fatty acids introduced into the duodenum have a 

 similar effect. 



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