EFFECT OF LOCAL STIMULATION. 551 



centre for the pancreatic secretion in the semilunar ganglion, there is 

 even greater difficulty in associating such a centre with any other 

 neighbouring structure, or in admitting that, as Popielski considers, it 

 may be placed in the walls of the pylorus. 



The conditions under which local stimulation provokes the 

 flow of pancreatic juice. As stated in the last section, a secretion 

 of the pancreatic juice, dependent upon integrity of the nerve connec- 

 tions, can be brought about by the action of certain substances upon the 

 mucous membrane of the stomach or duodenum. Thus it was long ago 

 noticed that injection of ether into the stomach will cause a flow of 

 pancreatic juice, the juice having characters corresponding to the par- 

 ticular stage of digestion in which the flow is brought about. 1 More 

 recently, other substances have been found to similarly affect the secre- 

 tion. If mineral acid, or even organic acids such as acetic and lactic, 

 be brought into contact with the duodenal mucous membrane, a secre- 

 tion will result. Since alkaline substances have not the same effect, 

 Dolinski 2 considers that the acid products of gastric digestion bring 

 about their own neutralisation by inducing a flow of alkaline pancreatic 

 juice when they enter the small intestine. Dolinski also found that 

 fat excited reflexly a pancreatic secretion, and that alcohol was also 

 effective in this direction, but only to a moderate degree. Gottlieb 3 

 agrees that reflexly induced secretion starts generally by stimulation of 

 the duodenal mucous membrane. Becker 4 studied the effect upon the 

 secretion of the introduction into the stomach of . distilled water and 

 of various salts. The salts employed were various alkaline salts, 

 Carlsbad salts, sodium chloride, and " Essentouck " mineral water. 

 Becker found that distilled water exalted the secretion, whilst salts, 

 especially alkaline salts, diminished it, both in amount and in proteo- 

 lytic power. Sodium chloride in smaller doses was indifferent, in 

 larger doses it behaved as the alkaline salts. The better the 

 absorption the more marked the secretion. Water containing car- 

 bonic acid is more easily absorbed than simple distilled water, and, 

 correspondingly, the former excites a more plentiful secretion than the 

 latter. 



We see, then, that the ordinary progress of the food can account for 

 the secretion normally appearing ; further, that the acid contents of the 

 stomach, when passed into the duodenum, may cause a powerful secretion, 

 and that alkaline salts in the stomach diminish the secretion. 



The ferments of the pancreatic juice and their antecedents. 

 Extracts made from the pancreas of many animals, and the pancreatic 

 juice obtained by the establishment of fistulae, possess the power of 

 changing different foodstuffs. Heidenhain 5 showed in 1875 that there 

 could be obtained from the pancreas a substance from which the proteo- 

 lytic ferment could be derived, but which did not actually possess 

 proteolytic activity. This substance he called " zymogen," but since we 

 are acquainted with substances having similar relations to other enzymes, 

 it is better to retain the name zymogen for the whole class, and to refer 

 each individual precursor by a name associated with the particular 

 ferment. We thus speak of the particular zymogen of the proteolytic 

 enzyme of the pancreas as trypsinogen. 



1 Kiihne, "Lehrbtich der physiol. Cliem." 2 Op. cit. 3 Op. cit. 



4 Arch, de sc. UoL, St. P<tersbourg, 1893, vol. ii. 



5 Arch.f. d. f/es. Physiol. , Bonn, 1875, Bd. x. 



