" DIGESTION IN THE SMALL INTESTINE. 385 



selves to be concentrated to a syrupy consistency. The aqueous solution gives 

 a precipitate with barium chloride, which at first dissolves again, but with more 

 barium solution a lumpy barium salt separates, which soon changes to a tough, 

 shiny, silky mass. The salts of this acid have a very bitter taste, which is not, 

 however, as intense as that of the A-acid salts. The composition of the acid could 

 not, as yet, be determined. Analysis proved that the percentage of carbon is 

 much less in the B-acid than in the A-acid, .whereas the percentage of nitrogen is 

 about equal in both. By continued treatment with alcohol, the B-acid yields 

 cholalic acid. In how far this acid corresponds to the one obtained in a similar 

 manner from the A-acid has not yet been determined. 



Various methods have been proposed for the separation of these salts from 

 the bile, of which only the following will be given. The bile from the gall-blad- 

 der of an ox should be evaporated to one-fourth its volume over a water bath, 

 rubbed up to a thick paste with animal charcoal, and completely dried at 100 C. 

 The hot mass should then be thrown into absolute alcohol, well shaken repeat- 

 edly, allowed to stand for two or three hours, and then filtered. A part of the 

 alcohol may be removed from the filtrate by distillation, and the bile salts may 

 then be precipitated, in the form of a resinous syrup, by the addition of a large 

 excess of ether. After standing a variable time, from one or two days to a week 

 or more, the time depending upon the anhydrous character of the alcohol and 

 ether, the so-called Platner's crystallized bile separates in a mass of glistening 

 needles. This crystallized bile consists of a mixture of taurocholate and glyco- 

 cholate of sodium. 



These salts are insoluble in ether and readily soluble in alcohol and 

 water. Their aqueous solutions have a decided alkaline reaction, and 

 rotate the plane of polarized light to the right. Both these salts are 

 highly deliquescent, and when exposed to the atmosphere the crystals 

 absorb the mixture and break down into a thick, tenacious S3*rup. 



To separate the two individual bile acids from each other, this mixture of 

 crystallized bile may be dissolved in a small volume of water, a little ether added, 

 and then dilute sulphuric acid. After stirring well, glycocholic acid crystallizes 

 in shining needles, the taurocholic acid remaining in solution. The crj'stals may 

 be collected on a filter, washed with water, dissolved in dilute spirits, and pre- 

 cipitated with excess of ether. "Or to the solution of Platner's crystals add 

 neutral and then a little basic lead acetate, when glycocholate of lead will be 

 thrown down. Collect on a filter, wash, and dissolve in hot alcohol, and remove 

 the lead by passing a current of sulphuretted hydrogen ; filter, and by the careful 

 addition of water to the alcoholic filtrate, crystals will be deposited. To the 

 previous filtrate from the glycocholate of lead add acetate of lead and ammonia ; 

 glycocholate and taurocholate of lead will be precipitated, and may be washed 

 and decomposed, as with the glycocholate." In the bile of oxen from certain 

 districts, glycocholic acid rapidly crystallizes on the addition of fivec.c. of hydro- 

 chloric acid and thirty c.c. of ether to each five hundred c.c. of bile. In other 

 .specimens this process entirely fails. No satisfactory explanation of this peculi- 

 arity has ever been given, though Hoppe-Seyler suggests that the acid removes 

 the base from the glycocholate, and the liberated glycocholate acid, being insoluble 

 in water, is precipitated. If this were the explanation, the process should invari- 

 ably succeed ; such is not, however, the fact. 



The test for these two acids is known as Pettenkofer's reaction for biliary 

 acids. If a little cane-sugar in strong solution is added to a small quantity of bile 

 in a test-tube, gently warmed to about 60 C , and then an equal volume of strong 

 sulphuric acid allowed to flow down the side of the tube, a bright-purple color 

 forms above the level of the acid. This test may be even better shown by pre- 

 paring the bile as before (solution of Platner s crystals), warming gently, with a 

 cane-sugar syrup, then shaking well until a layer of foam forms on the upper 

 surface. If a small amount of sulphuric acid is poured down the inside of the 

 tube, the froth on the surface of the bile becomes bright purple in color ; or bile 

 may be diluted with cane-sugar solution, and a piece of filter-paper dipped into it 



25 



