250 PANCREATIC JUICE. [BOOK n. 



over when bile, or a solution of bile-salts, is added to a fluid con- 

 taining the products of gastric digestion, a precipitate takes place, 

 consisting of parapeptone, peptone and bile salts. The precipitate 

 however is redissolved in an excess of bile or solution of bile-salts. 

 Concerning the purpose of this precipitation, which actually takes 

 place in the duodenum, we shall speak hereafter. 



With regard to the action of bile on fats, the following state- 

 ments may be made : 



Bile has a slight solvent action on fats, as seen in its use by 

 painters. It has by itself a slight but only slight emulsifying 

 power: a mixture of oil and bile separate after shaking rather 

 less rapidly than a mixture of oil and water. With free fatty acids, 

 bile forms soaps. It is moreover a solvent of solid soaps, and it 

 would appear that the emulsion of fats is under certain circum- 

 stances at all events facilitated by the presence of soaps in solution. 

 Hence bile is probably of much greater use as an emulsion agent 

 when mixed with pancreatic juice than when acting by itself alone. 

 To this point we shall return. Lastly, the passage of fats through 

 membranes is assisted by wetting the membranes with bile, or 

 with a solution of bile-salts. Oil passes with considerable ease 

 through a filter-paper kept wet with a solution of bile-salts, where- 

 as it passes with extreme difficulty through one kept constantly 

 wet with distilled water. 



Lastly bile possesses so-called antiseptic qualities. Out of the 

 body its presence hinders various putrefactive processes ; and when 

 it is prevented from flowing into the alimentary canal, the contents 

 of the intestine undergo changes different from those which take 

 place under normal conditions, and leading to the appearance of 

 various products, especially of ill-smelling gases. 



These various actions of bile seem to be dependent on the bile 

 salts and not on the pigmentary or other constituents. 



Pancreatic Juice. 



Natural healthy pancreatic juice obtained by means of a tem- 

 porary pancreatic fistula differs from the preceding fluids in the 

 comparatively large quantity of proteids which it contains. Its 

 composition varies according to the rate of secretion, for, with the 

 more rapid flow, the increase of total solids does not keep pace 

 with that of the water, though the ash remains remarkably 

 constant. 



By an incision through the linea alba the pancreatic duct (or ducts) 

 can easily be found either in the rabbit or in the dog, and a cannula se- 

 cured in it. There is no difficulty about a temporary fistula; but 



