408 



FOOD AND DIGESTION 



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

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

 due to their action, would be found, notably indol, phenols, and volatile 

 fatty acids. 



IV. BILE AND INTESTINAL JUICE. 



24. 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. 



BileSalts. 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 

 nitrate, 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 and absorption of fat and 

 fatty acids. 



25. Intestinal Juice. The secretion of the mucous membrane of the 

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

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



