DIGESTION AND ABSORPTION 175 



filter. To one portion (I) of filtrate add HC1. The yellow pre- 

 cipitate is glycocholic acid. 



"To the other portion (II) of the filtrate add lead acetate, which 

 throws down lead glycocholate. Remove this by filtration, and to the 

 filtrate add solution of basic lead acetate, which gives a further pre- 

 cipitation of lead taurocholate." Chemical Physiology, Long, p. 119. 



(c) Gmelin's Test for Bile Pigments. To a few cubic centimetres 

 of strong nitric acid containing nitrous acid carefully add dilute bile. 

 At the junction of the liquids a play of colors, green, blue, violet, red, 

 and yellow, will be noted; the green being next to the bile and the 

 yellow next to the acid. This delicate and most reliable test may 

 be applied to any liquid suspected of containing bile. 



(d) The reaction of bile is found to be distinctly alkaline. 



3. Experiments and Observations, (a) The Action of Pancreatic 

 Juice upon Foods. (1) To raw or cooked starch add in one beaker 

 aqueous extract of pancreas (a) ; in another add artificial pancreatic 

 juice (6); place the mixtures in the incubator; after a short time 

 test for reducing sugar. Pancreatic juice contains an amylolytic ferment* 



(2) Subject fibrin to the action of both of the pancreatic prepara- 

 tions. Pancreatic juice contains a proteolytic ferment. 



(3) Boil fresh milk and mix it with an equal bulk of the aqueous 

 extract of pancreas and put the mixture into the incubator. Put 

 also into the incubator boiled milk diluted with an equal volume of 

 distilled water. The milk which is mixed with the pancreatic juice 

 will curdle much sooner than the other. Pancreatic juice contains 

 a milk-curdling ferment. 



(4) Mix 5 c.c. or 6 c.c. of neutral olive oil with an equal volume of 

 aqueous extract of pancreas; shake the mixture vigorously. No 

 emulsion is formed. Place one-half of the mixture in the incubator. 

 After a few hours any undigested oil may be emulsionized on shak- 

 ing, or fresh oil may be emulsified. Explain. 



(5) To the second part of the mixture add 3 c.c. bile; shake the 

 mixture vigorously. A good emulsion is formed. How is this emul- 

 sion formed ? What factor of an emulsion does the bile add ? What 

 is the relation of experiment (5) to experiment (4) ? Pancreatic juice 

 contains a fat-splitting ferment whose action liberates fatty acids. 



(6) The Action of Bile upon Foods. (6) To starch paste add several 

 volumes of dilute bile. Result ? 



(7) To fibrin add dilute bile. Result? 



(8) To oil which contains free fatty acid add bile; shake the mix- 

 ture vigorously. Result? 



(9) To neutral oil add bile; shake the mixture vigorously. What 

 is the result? Allow the mixture. to stand in the incubator. After 

 several hours shake the mixture. Is an emulsion formed? 



(10) Summarize the results of the foregoing experiments, formu- 

 lating a series of conclusions regarding the action of pancreatic juice; 

 the action of bile and their combined action on each class of food. 



