CH. XI.] BILE SALTS. 265 



Taurine is derived from a similar product, cysteine. 

 CH 2 SH CH 2 .SO 3 H 



CH.NH 2 -> CH 2 .NH 2 



COOH 



Cysteine. Taurine. 



The bile acids are hydrolysed into their constituents 

 by boiling acids and also by the intestinal bacteria. 



The bile salts are soluble in water and alcohol, in- 

 soluble in ether. 



Their solutions have a remarkably low surface tension. 

 (See Hay's test.) 



They have the following functions : 



1 . They have a marked adjuvant action on pancreatic 

 lipase. (See Ex. 167.) 



2. They are solvents for the fatty acids and markedly 

 increase the absorption of fats. 



3. They thus help to remove the fatty film sur- 

 rounding the protein, and allow the proteolytic ferments 

 to act. In this way, by assisting the absorption of pro- 

 teins, they diminish bacterial decomposition. They are 

 not direct antiseptics. 



Preparation of Bile Salts. Mix 40 cc. of ox gall with enough animal 

 charcoal (about 10 grams.) to form a paste. Evaporate to dryness over a 

 water bath, stirring at intervals. Grind the residue in a mortar, transfer 

 it to a flask, add about 70 cc. of 96 per cent, or absolute alcohol and boil 

 on the water bath for 20 minutes. Cool and filter into a dry beaker. Add 

 ether to the filtrate till there is a slight permanent cloudiness. Cover the 

 beaker with a glass plate and allow it to stand in a cool place for 24 hours. 

 A crystalline mass of bile salts separates out. The crystals are filtered off and 

 allowed to dry in the air. 



For the following tests use diluted ox or sheep gall : 



315. Pettenkofer's test for bile salts. To 5 cc. of the 



solution add a small particle of cane-sugar and shake or* warm till 

 this has completely dissolved. To the cooled solution^add 5 cc. 

 of concentrated sulphuric acid, inclining the test-tube so that the 



