750 



PHYSIOLOGY OF DIGESTION AND SECRETION. 



in the duodenum as long as the stomach is empty. When, however, 

 a meal is taken the ejection of the chyme into the duodenum is fol- 

 lowed by an ejection of bile.* It would seem, therefore, that each 

 gush of chyme into the duodenum excites, probably by reflex action, a 

 contraction of the gall-bladder. The substances in the chyme that 

 are responsible for the stimulation have been investigated by Bruns. 

 He finds that acids, alkalies, and starches are ineffective, and con- 

 cludes that the reflex is due to the proteins and fats or some of the 

 products of their digestion. The gall-bladder has a muscular coat 



Fig. 273. 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.) 



of plain muscle, and records made of its contractions show that the 

 force exerted is quite small. According to Freese,f the maximal con- 

 traction does not exceed that necessary to overcome the hydrostatic 

 pressure of a column of water 220 mms. in height, a force, therefore, 

 which is about equivalent to the secretion pressure of bile as deter- 

 mined by Heidenhain. The innervation Of the gall-bladder and gall- 

 ducts has been studied especially by Doyon.f It would seem, from 



* See also Klodnizki, quoted from Maly's " Jahres-bericht der Thier- 

 chemie," 33, 617, 1904. 



t "Johns Hopkins Hospital Bulletin," June, 1905. 

 J Doyon, " Archives de physiologic, " 1894, p. 19. 



