SECRETION DIGESTION ABSORPTION. 



solution. Note the rate of pancreatic secretion for another period 

 of fifteen minutes. 



Allow ten minutes' rest. Then divide both vagus nerves and 

 stimulate with a weak tetanizing current. Note any change in the 

 rate of pancreatic flow. 



Repeat the injection of the acid. Is the same effect produced 

 that occurred after the first injection ? 



2. Action of Secretin (Bayliss and Starling). That the chief 

 stimulus to the elimination of pancreatic secretion is a chemical 

 one was demonstrated by Bayliss and Starling. They have found 

 that there is a substance present, in the mucous membrane of 

 the upper part of the small intestine chiefly, which they have 

 termed prosecretin. This, in the presence of hydrochloric acid, or 

 other acids to a less extent, is changed to another substance, se- 

 cretin, which is absorbed, passes to the pancreas, and there acts as 

 a stimulus to the elimination of pancreatic juice. 



An active secretin extract is prepared as follows: Cut out a dog's 

 duodenum and jejunum. Slit open the bowel. Wash thoroughly 

 with water. Scrape off the mucous membrane. Grind this with 

 sand and a little o.4-per-cent HC1 in a mortar. Add three times its 

 volume of o.4-per-cent HC1 and allow to stand for fifteen to twenty 

 minutes. Bring to a boil in a porcelain capsule, and while boiling 

 neutralize and render slightly alkaline with strong NaOH. Acidify 

 slightly with acetic acid, strain through muslin, and filter. 



Isolate and introduce a cannula into the central end of the fem- 

 oral vein of the dog of experiment i. While a record of flow of 

 the pancreatic juice is being taken, introduce into the vein 5 c.c. 

 of the secretin extract prepared as described above. Note the re- 

 sult on the rate of elimination of the pancreatic secretion. 



Repeat the injection several times, allowing a period of rest be- 

 tween injections. 



