102 PHYSIOLOGY. 



inhibitory fibers of the secretion, as well as secretory. He believes 

 that secretory fibers also run in the sympathetic, not only for the 

 pancreas, but also for the stomach. 



The usual method of obtaining pancreatic juice for experimental 

 purposes is by insertion of a cannula or by a fistula into the duct of 

 Wirsung. By this method practically normal secretion is procured, 

 whose composition is variable at different times, depending upon 

 whether the fluid is collected three or four hours, or two or three 

 days, after the operation. The secretion examined shortly after the 

 operation is meager in quantity, though rich in solids; that collected 

 a day or two later is more copious, but contains a smaller proportion 

 of solid constituents. This is probably due to inflammatory changes 

 in the pancreas as a result of the operation. The pancreatic juice 

 examined is usually obtained from dogs, human secretions of the 

 gland having been but rarely analyzed, and it has never been obtained 

 under quite normal conditions. Most experiments are performed 

 with the aid of an artificial juice made by mixing a weak solution (1 

 per cent, sodium carbonate) with a glycerin extract of pancreas. It 

 is usual to treat the pancreas with a dilute acid several hours previous 

 to its being mixed with glycerin to convert the zymogen, or mother- 

 substance, trypsinogen, into the ferment, trypsin. 



Normally, the pancreatic juice is colorless, viscid, and gummy; 

 it flows in large, pearl-like drops, which become foamy on agitation. 

 The fluid is without odor, and gives to the tongue an impression of a 

 viscid liquid and a taste like that of salt. The reaction is always 

 alkaline; its specific gravity about 1.030. 



In consequence of the removal of a pancreatic tumor Zawadski 

 obtained human pancreatic juice through the fistula remaining, wlrch 

 possessed powerful digestive properties, and found it to be made up of 

 the following composition in a thousand parts: 135.9 parts were of 

 solid nature, the remaining ones being water. Of the solid portions, 

 92 were proteids, 3.4 parts were inorganic in nature, while the re- 

 mainder were organic substances soluble in alcohol. The figures rep- 

 senting the quantities of secretion in twenty-four hours are very 

 various as given by different observers, but it has been roughly esti- 

 mated to average about 1 pound. 



The flow of pancreatic juice is somewhat as follows : Before the 

 meal is finished there begins the secretion, which reaches its maximum 

 point at about the third hour. After this the secretion sinks till about 

 the sixth or seventh hour, when it increases to the ninth or eleventh 

 hour, only to sink gradually to the eighteenth or twentieth. When 



