358 PANCREATIC JUICE. [BOOK n. 



of the pancreatic juice. To peptic action it is distinctly antago- 

 nistic ; the presence of a sufficient quantity of bile renders gastric 

 juice inert towards proteids. Moreover when bile, or a solution of 

 bile-salts, is added to a fluid containing the products of gastric di- 

 gestion, a precipitate takes place, consisting of parapeptone (when 

 present), peptone, pepsin and bile salts. The precipitate is redis- 

 solved in an excess of bile or solution of bile-salts ; but the pepsin 

 though redissolved remains inert towards proteids. This precipi- 

 tation actually does take place in the duodenum, and we shall 

 speak of it again later on. 



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 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 circumstances at all events facilitated by the pres- 

 ence 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 will pass to a certain extent through a filter-paper kept wet 

 with a solution of bile-salts, whereas it will not pass or passes 

 with extreme difficulty through one kept constantly wet with 

 distilled water. 



Bile possesses some 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. 



209. Natural healthy pancreatic juice obtained by means of 

 a temporary pancreatic fistula differs from the digestive juices of 

 which we have already spoken, 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 

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



