SECRETION. 



177 



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 



\ 



\ 



<? / a. 3 * s 6 <r 8 9 JO it it, /3 /* Is 16 // fS 



FIG. 78. Curve 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 intestine. 

 Gottlieb l finds that in rabbits the pancreatic secretion is very greatly accel- 

 erated by stimulants such as oil of mustard, pepper, acids, or alkalies intro- 

 duced into the stomach or duodenum, and Doliusky, 2 working upon dogs 

 under more favorable experimental conditions 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 gastric secretion is perhaps the most effective stimulus to the pan- 

 creatic gland, and that in this way the flow of gastric juice in ordinary diges- 

 tion starts the pancreatic gland into activity. Whether the acid acts after 

 absorption into the blood, or stimulates the sensory fibres of the mucous mem- 

 brane and thus reflexly affects the pancreas through its secretory nerves, is not 

 definitely known, but the probabilities are in favor of the latter view. It is 

 probable also that the acid acts mainly upon the sensory fibres of the mucous 

 membrane of the duodenum rather than upon the gastric membrane. 



1 Archiv fur experimenteUe Pathologie und Pharmakologie, 1894, Bd. 33, p. 273. 



2 Archives des Sciences biologiques, St. Petersburg, 1895, vol. iii. p. 399. 

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