On the Functions of the Bile as a Solvent. 



67 



carried in solution to the liver cells to be there excreted, as to how 

 they are preserved in solution in the bile, and as to the extent to which 

 each of them is soluble in that fluid. 



Experiments were accordingly arranged to test the powers of the 

 bile salts as a solvent for these two substances, which taken in con- 

 junction with the known facts as to the reabsorption and circula- 

 tion in the blood of the bile salts cast a considerable light upon the 

 questions above outlined, and furnish a rational explanation of the 

 so-called " circulation of the bile." 



It is, in our opinion, in this property of acting as a solvent for sub- 

 stances which are insoluble in water, that bile has its main if not its 

 only function, both in excretion and absorption. 



Any other properties which have been ascribed to the bile are of 

 very minor importance compared to this one. It enables us in the 

 first place to explain clearly the part played by bile in fat absorption, 

 for our experiments show not only that the solubilities of the soaps are 

 considerably increased, but, which is of more importance still, that 

 they are dissolved by the bile in a different physical condition from 

 that in which they are held in solution by water alone, as is shown by 

 the altered physical properties of the solution. Further, free fatty acid 

 could not be held in solution in the intestine in the absence of bile. 

 Again, it is impossible to see how such substances as cholestearin and 

 lecithin could be excreted in the absence of some vehicle conferring 

 solubility upon them. 



Experimental Methods. 



The bile salts used in our experiments were prepared by a usual 

 modification of Plattner's method from ox bile. The bile was con- 

 centrated to a syrup on a water-bath, mixed into a paste with animal 

 charcoal, extracted with absolute alcohol, filtered, and ether added to 

 commencing precipitation. On standing, the bile salts were obtained 

 in crystalline spherules, and these were purified by dissolving in 

 alcohol and reprecipitating with ether. 



The mixed sodium soaps employed were obtained by saponifying 

 beef suet. Much labour was expended on various attempts to prepare 

 these in a pure form ; such as obtaining the free fatty acids in ethereal 

 solution and neutralising with alcoholic potash, or extracting the soaps 

 with hot alcohol in a Soxhlet apparatus and cooling out from the 

 alcohol. These methods have practical difficulties, however, on 

 account of the varying solubilities of the constituent salts in the organic 

 solvents. Accordingly, a simpler method was found to yield better 

 results. The fat was first saponified by slight excess of caustic soda, 

 and the mixture of soaps thrown into a large excess of cold water,* 



* Saturated solution of sodium chloride was at first used, but it was found that 

 the mixed sodium soaps were so insoluble in cold water that no such saline 



