784 PHYSIOLOGY OF DIGESTION AND SECRETION. 



of the secretion are formed they are frequently designated as zymo- 

 gen granules. The pancreas contains also certain peculiar groups of 

 cells, the islands (or bodies) of Langerhans. These cells probably 

 have nothing to do with the digestive activity of the pancreas. 

 Their supposed function is referred to in the sections on Internal 

 Secretions and Nutrition. 



Composition of the Secretion. — ^The pancreatic secretion is an 

 alkaline liquid wMch in some animals is thin and limpid, in others 

 thick and glairy. The secretion in man belongs to the former 

 type ; it is described as water-clear and as having a specific gravity of 

 1.0075. The secretion may be collected by opening the abdomen 

 and inserting a cannula directly into the duct, or a permanent 

 fistula may be made by the method of Pawlow. This method, 

 applicable to the dog, consists in cutting out a small portion of 

 the duodenum where the pancreatic duct opens and then suturing 

 this piece, the mucous membrane outward, into the abdominal 

 wall. The secretion in this case pours out upon the exterior and may 

 be collected. The animal, however, suffers nutritive disturbances 

 from the loss of the secretion, and requires careful dieting and atten- 

 tion. The secretion of the human pancreas has been collected in 

 several cases in which it was necessary to drain off the pancreatic 

 juice to the exterior. From the observations made in one case* it 

 appears that the secretion in man is quite abundant, amount- 

 ing to 500 to 800 c.c. per day. In the cow (Delezenne) from 1| to 2 

 liters may be collected in the course of a day. The secretion pos- 

 sesses a strong alkaline reaction, due to the presence of sodium 

 carbonate; it also contains a small amount of coagulable protein 

 and a number of organic substances in traces. The important 

 constituents, however, are three enzymes or their zymogens, — 

 namely, trypsin, a proteolytic enzyme; pancreatic diastase (amyl- 

 ase), an amylolytic enzyme; and lipase (steapsin), a lipolytic 

 enzyme. Some authors state, also, that the secretion contains a 

 rennin enzyme. Glaessner reports that he got no evidence of this 

 last enzyme in human pancreatic juice. 



Secretory Nerve Fibers to the Pancreas. — The pancreas 

 receives its nerve supply immediately from the celiac plexus, but 

 stimulation of the nerves going to this plexus — namely, the splanch- 

 nics and the vagi — have given negative results in the hands of most 

 observers so far as the pancreatic secretion is concerned. Pawlow f 

 and his coworkers claim to have been more successful. Mechanical 

 stimulation or electrical stimulation of the vagus or splanchnic gave 



*See Glaessner, "Zeitschrift f. physiol. Chemie," 40, 465, 1903. Also 

 Wohlgemuth, "Biochem. Zeitschrift," 39, 302, 1912. 



t For modern work upon the pancreas and the literature see Pawlow, 

 "The Work of the Digestive Glands," translation by Thompson, 1902; Bay- 

 liss and Starling, "Journal of Physiology," 30, 61, 1904; Walter, "Archives 

 des sciences biologiques," 7, 1, 1899. 



