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AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



diminishes in quantity to the sixteenth or seventeenth hour, when it has 

 practically reached the zero point. In man, in whom the meals normally 

 occur at intervals of five to six hours, this curve of course would have a dif- 

 ferent form. The interesting fact, however, that the secretion starts very soon 



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Fig. 61.— < iirvi- of the secretion of pancreatic juice during digestion. The figures along the abscissa 

 represent hours after the beginning of digestion ; the figures along the ordinate represent the quantity 

 of this secretion in cubic centimeters. Curves of two experiments are given (after Heidenhain). 



after the beginning of gastric digestion is probably true for human beings, and 

 gives strong indication that the secretion is a reflex act. 



Recently a number of experiments have been reported which strengthen 

 the view that the normal secretion of the pancreas is reflexly excited by 

 stimuli acting upon the mucous membrane of the stomach or duodenum. 

 Dolinsky, 1 working upon dogs by Pawlow's methods, finds that acids are 

 particularly effective in arousing the pancreatic flow ; on the contrary, alkalies 

 in the stomach diminish the pancreatic secretion. Dolinsky believes that the 

 normal acidity of the gastric secretion is perhaps the most effective stimulus to 

 the pancreatic gland, and that in this way the flow of gastric juice in ordinary 

 digestion starts the pancreatic gland into activity. Whether the acid acts 

 after absorption into the blood, or stimulates the sensory fibres of the mucous 

 membrane, and thus reflexly affects the pancreas through its secretory 

 nerves, is not definitely known, but the probabilities arc in favor of the 

 latter view. It is probable also that the acid acts upon the sensory fibres 

 of the mucous membrane of the duodenum rather than upon the gastric 

 membrane. 



In addition to acids, it has been found that oils and water introduced into the 

 stomach also cause a flow of pancreatic juice, the stimulation occurring prob- 



1 Archives des Sciences biologiques, St. Petersburg, 1895, t. iii.'p. 399. 



