EFFECT OF LOCAL STIMULATION. 551 
centre for the pancreatic secretion in the semilunar ganglion, there is 
even greater ditliculty in associating such a centre with any other 
aeighbouring Btructure, 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 Baits, 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 fistula?, 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 Klihne, " Lehrbueh der physiol. Chem." - Op. eit. 3 Op. eit. 
4 Arch. desc. biol.. St. Petersbourg, 1893, vol. ii. 
3 Arch.f. d. ges. Physiol., Bonn, 1875. Bel. x. 
