On the Functions of the Bile as a Solvent. 



71 



employed as the solvent ; the amount of undissolved residue increases 

 as the amount of mixed soaps added is increased, but it is obvious to 

 the eye that a considerable amount of the later additions of soap are 

 being dissolved, and, further, a determination of the melting point of 

 the mixed fatty acids obtainable from the undissolved residue proves 

 that this consists chiefly of palmitates and stearates. 



This is interesting from the physiological point of view, since a 

 similar separation must take place in the intestine, and the oleates be 

 absorbed more readily and more rapidly than the palmitates and 

 stearates. 



Besults. 



1, Free Fatty Acids. — The mixed free fatty acids obtainable from 

 beef suet are practically insoluble in distilled water at body tempera- 

 ture. When as little as 0*1 per cent, is added, the greater part remains 

 undissolved in the form of melted globules ; but, on cooling down, a 

 faint opalescence in the fluid indicates a slight degree of solubility. A 

 5 per cent, solution of bile-salts dissolves - 5 per cent, of the mixed 

 acids, and a 5 per cent, solution of bile-salts phis 1 per cent, of lecithin 

 dissolves 0*7 per cent. The effect of the lecithin in increasing the 

 solubility is clearly seen by heating simultaneously in two test-tubes, 

 one containing bile-salts alone, and the other bile-salts plus lecithin, 

 0'5 per cent, of the fatty acids. The tube containing the lecithin clears 

 first, and on cooling the two tubes a heavy precipitate is obtained in 

 the case of the bile-salts only, and scarcely any precipitate in the solu- 

 tion containing lecithin in addition. 



Oleic acid has the following solubilities : — Distilled water less than 

 0*1 per cent. ; bile-salt solution, 0*5 per cent. ; bile-salt plus lecithin 

 solution, 4 per cent.* 



Palmitic acid, in distilled water, less than O'l per cent. ; in bile-salt 

 solution, O'l per cent. ; in bile-salt plus lecithin solution, 0*6 per cent. 



Stearic acid, in distilled water, less than 0*1 per cent.; in bile- salt 

 solution, less than O'l per cent. ; in bile-salt plus lecithin solution, 

 0'2 per cent. 



2. Sodium Soaps. — The mixed sodium soaps of beef suet, tested by 

 the supersaturation method, yield to distilled water 2*23 per cent., 

 and to ox bile (sp. gr. 1027) 3'69 per cent. The solubilities in the 

 other solvents of the mixed soaps was not determined, because the 

 constituents, for the reasons assigned above, are not taken up in pro- 

 portionate quantities, and hence the figures have little value as quanti- 

 tative results. 



The above figures consequently give merely the maximum uptake of 



* The bile-salt solutions employed invariably contained 5 per cent, of the 

 mixed bile-salts of ox bile, and the bile salt phis lecithin solutions 1 per cent, of 

 lecithin in addition. 



VOL. LXVIII. G 



