PANCREATIC DIGESTION 271 



phosphorus in organic combination, and various substances. In- 

 organic sulphates are absent or present only in traces. 



b. Bile Acids in the Form of Alkali Salts. 



1. Pettenkofer's test for bile salts. To 5 c.c. of bile add a few 

 grains of cane sugar or a few drops of cane sugar solution. With 

 a pipette (caution: do not draw acid into the mouth), add con- 

 centrated H 2 S0 4 to form a layer at the bottom, or allow 2-3 c.c. 

 of acid to run down the side of the tube. Note the red ring. 



2. Extraction of bile salts. Bile salts may be prepared by 

 heating bile, charcoal (enough to make the mixture fairly thick) 

 and 5 volumes of alcohol on the water bath for 20 minutes, re- 

 placing alcohol lost by evaporation. Filter off the liquid and add 

 ether in excess. Bile salts are precipitated. 



c. Bile Pigments. 



I. Gmelin's test. To about 5 c.c. of concentrated HN0 3 in a 

 test tube, add 2-3 c.c. of diluted bile, carefully, so that the two 

 liquids do not mix. Note the colored rings. 



d. Mucin and Pseudomucin. Bile is said, by some authorities 

 to contain mucin. On the addition of 5 volumes of alcohol to 

 bile a precipitate is formed. This is called pseudomucin, and is 

 believed by some to be a phosphoprotein. 



e. In addition to the above constituents, bile also contains 

 small amounts of fats, lecithin, phosphates, cholesterol, etc. 



II. Effect of Bile on Surface Tension. Fill one small beaker 

 with distilled water. To a second beaker, add bile diluted with 4 

 parts of water. Sprinkle a few grains of powdered sulphur over 

 each. In the beaker containing bile, the sulphur sinks to the bot- 

 tom. The surface tension of the water has been reduced so that 

 the surface film is no longer able to support the sulphur grains. 



III. Biliary Calculi, or Gall Stones, are of four kinds: 



a. Those made up of calcium, iron or copper combined with 



bile pigments. 



b. Cholesterm calculi. 



c. Calculi of calcium phosphate and carbonate. 



d. Calculi of combinations of the above. 



