430 OF FOOD, AND THE DIGESTIVE PROCESS. 



entericus" possesses a more energetic emulsifying power than the first of these 

 fluids alone; and it seems probable that, as in the conversion of starch, so in 

 the emulsification of fat, the intestinal fluid performs a very important part. 

 It would not seem unlikely that the qualities of these fluids (like those of the 

 saliva) may vary in different animals; and that the emulsifying power may be 

 limited in the rabbit, or nearly so, to the pancreatic fluid, the quantity of fat 

 which its natural food contains being small; whilst in the carnivorous animals, 

 whose natural food is more oleaginous, the provision for the digestion of fatty 

 matters may be more extensive. Of the amount of pancreatic fluid which is 

 daily secreted by Man, we have no other data for forming an estimate than 

 those afforded by the. observations of Frerichs; who collected from an ass, in" 

 45 minutes, 387? grains, and from a large dog, in 25 minutes, 46 grains. These 

 amounts, however, were poured forth while food was in the stomach and digestion 

 was going on; and it is probable that, at other times, the secreting process is 

 nearly or entirely suspended. 



453. The Duodenum receives not only the Pancreatic, but also the Biliary 

 secretion ; and from the constancy with which this fluid is poured into the upper 

 part of the intestinal tube, or even into the stomach itself, in all animals which 

 have any kind of hepatic apparatus, 1 it seems a legitimate inference that this 

 secretion is not purely excrementitious, but serves some important purpose in 

 the digestive process. It is not easy, however, to state with precision what this 

 purpose is. The result of many of the experiments which have been made to 

 determine it, are vitiated by the fact, that the pancreatic duct in most cases 

 discharges itself into the intestinal tube at the same point with the hepatic, and 

 has thus been frequently involved in operations performed upon it. As the 

 most important constituents of Bile have been already described ( 67 71), 

 and as the agency of the Liver as an assimilating and depurating organ will be 

 more appropriately considered elsewhere (CHAPS, vin. and xn.), we shall here 

 limit ourselves to the consideration of what may be regarded as the best esta- 

 blished facts in regard to the uses of the biliary secretion in the digestive pro- 

 cess. When its action is tested out of the body, by mingling it with the 

 different constituents of food, it is found to exert no change upon starchy sub- 

 stances whilst it is fresh ; though, when in a state of incipient decomposition, 

 it acts upon them as other animal substances do. It has no action upon cane 

 sugar, until it has stood a considerable length of time ; but then it converts it 

 into lactic acid. This change it speedily exerts, as do nearly all other animal 

 substances, upon grape sugar. It has no action on albuminous substances, even 

 when acidulated. And, although it will form an emulsion with oleaginous 

 matter, yet the emulsification is less complete than that which is effected by the 

 pancreatic fluid alone. 3 Hence it appears to be deficient in anything at all 

 similar to the peculiar ferments of the saliva, gastric juice, and pancreatic 

 secretion ; and its oflice in digestion must be of a different character from that 

 of either of those fluids. The nature of this oflice may be partly judged of 

 from what takes place when fresh bile is mingled with the product of gastric 

 digestion. The acid reaction of the latter is neutralized by the alkali of the 

 former, and a sort of precipitation takes place (as was originally noticed by Dr. 

 Beaumont), in which certain constituents of the bile fall down, and in which 

 also (according to M. Bernard) the albuminous matters that have been dissolved 

 and not yet absorbed, are for a time rendered insoluble, leaving the saccharine 

 matters in solution, and the oleaginous floating on the top. The admixture of 



1 See "Princ. of Phys., Gen. and Comp.," Am. Ed.,\% 583 588. The simplest con- 

 dition of the Liver, such as we meet with in the higher lladiata, and in the lower Articu- 

 lata and Mollusca, consists in a series of follicles lodged in the walls of the stomach and 

 of the upper part of the intestinal tube. 



2 Dr. Bence Jones, in the "Medical Times," July 5, 1851. 



