224 PHYSIOLOGY OF ALIMENTATION. 



vase-constrictor effects completely mask the secretory. 

 The two can be separated by mechanical stimulation of the 

 sympathetic. When this is done stimulation always leads 

 to an increased secretion from the gland, for, as is well known, 

 vaso-constrictor nerve fibres are not readily excited by 

 mechanical means. The two can also be separated by stim- 

 ulating the sympathetic several days after it has been divided. 

 The vaso-constrictor fibres are the first to degenerate, so that 

 only those influencing the secretory activity of the gland are 

 left to exhibit their characteristic effects. 



4. The Normal Excitants of the Pancreas. It has been 

 shown above that during a period of digestive inactivity the 

 pancreas secretes no juice; that after feeding, a large amount 

 of pancreatic juice is secreted. What determines this secre- 

 tion? The relation of the various inorganic constituents 

 of the food to the pancreatic flow has been studied by 

 BECKER l and DoLiNSKi. 2 



Acids of all kinds act as powerful excitants of the pan- 

 creatic secretion. If 250 c.c. of a 0.5 percent hydrochloric acid 

 solution, for example, are introduced by means of a catheter 

 into the stomach of a dog possessing a permanent pancreatic 

 fistula, the inactive pancreas begins to secrete within two or 

 three minutes. Within ten minutes the pancreatic flow 

 reaches its maximum and within the first hour some 80 c.c. 

 of juice may be collected. The rate of secretion steadily 

 falls, so that towards the end of the second hour only about 

 15 c.c. can be collected before the outflow ceases entirely. 

 If, instead of the hydrochloric acid solution, an equal amount 

 of water is injected into the stomach little or no pancreatic 

 juice is obtained, which shows that it is the acid which is 

 active. That at the end of such an experimental period the 

 pancreas is not exhausted can be readily proved by injecting 



1 BECKER: Archives des Sciences Biologiques, II, p. 433. PAWLOW'S 

 Work of the Digestive Glands. Translated by THOMPSON, London, 

 1902, p. 113. 



2 DOLINSKI: Arch, des Sci. Biolog., Ill, p. 399. 



