816 



PHYSIOLOGY OF DIGESTION AND SECRETION. 



this effect takes place when the nervous connections are severed, the 

 effect, as in the case of the pancreatic secretion, is explained by 

 assuming that the acid converts prosecretin to secretin, and this 

 latter after absorption into the blood acts upon the liver cells.* 

 A similar effect may be obtained by injecting secretin directly into 

 the blood. Since during a meal the stomach normally ejects acid 

 chyme into the duodenum, the importance of this secretin reaction 

 in adapting the secretion of bile to the period of digestion is evident. 

 The Ejection of Bile into the Duodenum — Function of the 

 Gall-bladder, — Although the bile is formed more or less continu- 

 ously, it enters the duodenum periodically during the time of digestion. 

 The secretion during the intervening periods is prevented from enter- 

 ing the duodenum apparently by the fact that the opening of the 



Fig. 297. — Curves showing the velocity of secretion of bile into the duodenum on 

 (1) a diet of milk, uppermost curve; (2) a diet of meat, middle curve; (3) a diet of bread, 

 lowest curve. The divisions on the abscissa represent intervals of thirty minutes; the 

 figures on the ordinates represent the volume of secretion in cubic centimeters. — (Bruns.) 



common bile-duct is closed by a sphincter. The secretion, therefore, 

 backs up into the gall-bladder. According to Bruns. f no bile appears 

 in the duodenum as long as the stomach is empty. When, how- 

 ever, a meal is taken, the ejection of the chyme into the duode- 



* See Falloise, quoted in Maly's " Jahres-bericht der Thier-chemie," 33, 

 611, 1904. 



t "Archives des sciences biologiques," 7, 87, 1899. 



