186 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



cent, alcoholic solution of thiophene and shake. Replace the tube in the 

 boiling water ; as the mixture gets warm a cherry -red colour develops. 



4. Demonstration of Pancreatic Secretion. In an ansesthetised dog insert 

 a cannula into the main pancreatic duct, and collect the juice in a suitable 

 vessel. Inject some 0'4-per-cent. hydrochloric acid into the duodenum, and 

 note after some minutes the abundant flow of pancreatic juice. Next 

 ligature off and remove two or three feet of the upper part of the small 

 intestine, wash out the contents and slit it open ; scrape oft' the mucous 

 membrane with the back of a scalpel ; preserve a small quantity of the 

 scrapings for future use and label this A. Grind up the remainder in a 

 mortar with clean sand or powdered glass, and add 0'4 per cent, hydrochloric 

 acid. Transfer the mixture to a flask, boil thoroughly, and when cool 

 neutralise with a little caustic soda solution. Filter ; the filtrate contains 

 secretin, which has been formed by the acid from the pro-secretin of the 

 intestinal epithelium. Inject some of this solution through a cannula into 

 the external jugular vein of the dog, and an abundant flow of pancreatic 

 juice is an almost immediate result. 



5. Characters of the juice so obtained : 



(a) It is a clear, colourless fluid, and very strongly alkaline. 



(b) Mixed with starch solution and kept at 40 C. dextrin and maltose are 

 rapidly formed. 



(c) Mixed with milk there may be some curdling produced, but the most 

 marked effect is that the milk rapidly becomes acid, and a smell of fatty 

 acids is noticeable. 



(d) Added to fibrin and kept at 40 protein digestion occurs very slowly; 

 next day, however, the fibrin will be in large measure digested. 



(e) Mix some of the pancreatic juice with the scraping of the intestine 

 which was preserved and labelled A. Then add fibrin. The fluid is now 

 strongly proteolytic, and at 40 C. the fibrin rapidly dissolves ; trypsin has 

 been liberated from the trypsinogen of the juice by the intestinal entero- 

 kinase. 



6. Products of Pancreatic Digestion of Proteins. A pancreatic digest 

 should be prepared beforehand by the demonstrator. This may be done by 

 digesting a quantity of protein with artificial pancreatic juice, if the natural 

 juice prepared by the action of secretin is not available ; in the latter case 

 the addition of intestinal epithelium (entero-kinase) should not be forgotten. 

 Unless an antiseptic has been added putrefaction will also occur, and its 

 odour will be very perceptible after the mixture has been placed in the warm 

 chamber for some time. 



A very good mixture for the purpose will be found to be the following : 



100 grammes of plasmon (caseinogen). 

 10 grammes of sodium carbonate. 



1 litre of water. 

 25 c.c. of Benger's liquor pancreaticus. 



0*5 gramme sodium fluoride. 



3 c.c. chloroform. 



The last two items on the list are added to prevent putrefaction, 



