360 FOOD AND DIGESTION 



ficial pancreatic juice add 25 grams of moist fibrin and place in a water bath 

 at 40 C., add 7 c.c. of chloroform to prevent putrefactive changes. After three 

 or four hours filter off 80 c.c. and place the remainder on the water bath for 

 two or three days. Test the filtrate for alkali albumin, albumoses, and pep- 

 tones, by the method outlined in experiment 14 above. 



Filter the second portion and concentrate to a syrupy mass on the water 

 bath. Crystals make their appearance. Pour off the fluid, wash the crystals 

 with cold water, and examine under the microscope for sheaves of tyrosin. 

 The filtrate contains leucin. 



If the digestion had been allowed to proceed without the chloroform, 

 bacteria would have appeared in the solution, and proteid cleavage products, 

 due to their action, would be found, notably indol. 



IV. BILE AND INTESTINAL JUICE. 



23. Bile. Secure bile from the gall-bladder of a pig or dog, or, if 

 it is possible, a sample of human bile. Test the reaction which, in fresh 

 bile, is neutral. Test for mucin; albumin; and for iron; hydrochloric acid 

 and ferrocyanide of potassium give a blue color when iron is present. 



Bile Salts. Evaporate 10 c.c. of bile to complete dryness, mix with animal 

 charcoal, add 50 c.c. of absolute alcohol, filter; add an excess of ether to the 

 filtrate, which gives a white precipitate of bile salts. Crystals will form on 

 standing in a well-stoppered flask for a day or two. 



Bile Acids. A drop of syrup of cane-sugar in a test tube of bile forms a 

 deep red-purple color at the line of separation from concentrated sulphuric 

 acid. Furfur aldehyde with cholalic acid gives the color. 



Bile Pigments. With i c.c. of bile in a test tube strong nitroso-nitric 

 acid produces a play of colors beginning with green, blue, red, and yellow 

 Gmelin's test. 



Bile does not contain digestive enzymes, but the bile wets the mucous 

 surface of the intestine and facilitates the solution of fats and fatty acids. 



24. Intestinal Juice. The secretion of the mucous membrane 

 of the small intestine has been proven to have a weak digestive action on pro- 

 teids and perhaps on starches. It can be obtained from an intestinal fistula. 

 Its chief digestive importance consists in the presence of the activating enzyme, 

 enterokinase. Enterokinase can be prepared by extracting the mucous mem- 

 brane of the small intestine by the method outlined for making a pancreatic 

 extract. 



To two test tubes containing 5 c.c. of artificial pancreatic juice, or pref- 

 erably containing secretin pancreatic juice, add flocks of fibrin. Keep one 

 for the control, to the other add 2 c.c. of enterokinase solution. The test tube 

 containing enterokinase will digest more rapidly and more effectively than 

 the other. 



