DIGESTION AND ABSORPTION IN THE INTESTINES. 



785 



them a marked flow of pancreatic juice, but when the latter form of 

 stimulus was used upon the splanchnic, it was necessary to cut 

 the nerve some days previously in order that the vasoconstrictor 

 fibers might degenerate. The secretion provoked by stimulation 

 of the vagus is more easily obtained when the stimulus is applied 

 to the nerve in the thorax below the origin of the branches to the 

 neart. The secretion obtained upon stimulation of the nerves 

 is characterized, as in the case of the gastric glands, by a long 

 latent period of some minutes, — a fact that is explained, although 

 not satisfactorily, on the assumption that the nerve trunks stimu- 



Fig. 296. — Four curves of the secretion of the pancreatic juice, the three in black, 

 from Walter, showing the secretion in dogs on different diets: (1) on 600 c.c. of milk; (2) 

 on 250 gms. bread; (3) on 100 gmL. of meat- The curve in red, from Glaessner, shows 

 the secretion in man on a mixed diet, soup, meat, and bread. The figures, 1, 2, 3 etc., 

 along the abscissa indicate hours after the beginning of the meal. The figures along the 

 ordinates indicate the quantity of the secretion in cubic centimeters. 



lated contain both secretory and inhibitory fibers and that the 

 antagonistic action of the latter delays the appearance of the 

 secretion. These observations have been taken as proof of the 

 existence of secretory nerve fibers to the pancreas, the fibers 

 running chiefly in the vagus nerve. 



The Curve of Secretion. — The rate of flow of the pancreatic 

 juice with reference to the period of digestion has been determined 

 by a number of observers. In the careful experiments reported by 

 Walter it is shown that the quantity of secretion is dependent to a 

 considerable extent upon the character of the food. Thus, the 

 flow is more abundant and reaches its maximum sooner after ^ 



50 



