358 FOOD AND DIGESTION 



the milk is first coagulated, then slowly dissolved or digested. This clotting 

 is due to the special coagulating enzyme, rennin. 



III. PANCREATIC JUICE AND PANCREATIC DIGESTION. 



1 6. The Secretion of Pancreatic Juice. If a dog containing a pan- 

 creatic fistula made by Pawlow's method is available, then try the experi- 

 ment of feeding the animal and noting the rate of secretion of pancreatic 

 juice through a period of two hours. When the gastric digestion has proceeded 

 to the point where the acid chyme may be supposed to have entered the duo- 

 denum, then a sharp increase in the flow of pancreatic juice takes place. This 

 increased activity will last through a period of two or three hours or more. 

 It is produced either by nerve reflexes (Pawlow) or by the influence of the 

 secretion produced by the gastric mucous membrane when stimulated by acid. 



17. Influence of Secretin on the Rate of Secretion. Make an ex- 

 tract of the intestinal mucous membrane, preferably from the duodenum, 

 by scraping off the membrane, grinding it to a pulp, and extracting it over a 

 water bath in 0.2 per cent hydrocholoric acid, and filtering. 



Anesthetize a large dog, open the abdomen, isolate the pancreatic duct, 

 introduce a cannula, and arrange for the collection of pancreatic juice. Intro- 

 duce a cannula into the saphenous vein and connect it with a buret containing 

 the extract of secretin already prepared. Inject 5~c.c. quantities of the secretin 

 solution into the vein at intervals of ten minutes. Measure the rate of secretion 

 of pancreatic juice by counting the drops per minute, or if the secretion is 

 rapid enough, by collecting it at intervals of five or ten minutes and measuring 

 it in a graduated pipet. 



This method will often yield enough pancreatic juice in the course of a 

 couple of hours to make the pancreatic experiments which follow. Bayless 

 and Starling call it secretin juice. 



1 8. Chemical Characters of Pancreatic Juice. Test the reaction, 

 proteid, salt, etc., content of the sample of pancreatic juice collected in the 

 last experiment. 



19. Artifical Pancreatic Juice. Artificial pancreatic juice can be 

 prepared from the pancreas by grinding and macerating and extracting a 

 pancreas with water or glycerin, as described for the gastric glands in experi- 

 ment ii above. Commercial preparations of pancreatic enzyme can be ob- 

 tained on the market. A solution of glycerin extract of pancreatic gland or 

 of commerical pancreatin in 0.2 per cent sodium carbonate is known as arti- 

 ficial pancreatic juice. 



20. The Enzymes of Pancreatic Juice. The pancreatic juice con- 

 tains enzymes which have exerted a digestive action on starches, fats, and 

 proteids. This fact can be tested as follows : a, To 5"c.c. of artificial pancreatic 

 juice add 2 c.c. of i percent starch paste, mix and set in the water bath at 40 C. 



