ACTION OF THE BILE IN DIGESTION. 



277 



In some instances, pieces of tripe which had been fed to the animal were recognizable in 

 the fasces " by their aspect, because of their slight alteration." The voracious appetite, 

 progressive emaciation, and the passage of all classes of alimentary substances in the 

 faeces, after this operation, demonstrate conclusively the great importance of the pancre- 

 atic juice in digestion. But, when we inquire into the precise mode of action of this 

 fluid upon the albuminoids, the question becomes one of great difficulty. If the bile be 

 shut off from the intestine and discharged externally by a fistulous opening, the same 

 voracity and emaciation are observed ; and yet there is no single alimentary substance 

 upon which the bile, of itself, can be shown to exert a decided digestive action. Farther- 

 more, the pancreatic juice is evidently calculated to act upon alimentary principles after 

 they have been subjected to the action of the stomach, a preparation which is absolutely 

 essential to proper intestinal digestion; and, once passed into the intestine, the food 

 comes in contact with a mixture of pancreatic juice, intestinal juice, and bile. We have 

 to study, therefore, the special action of the pancreatic secretion upon the albuminoids, 

 as far as it can be isolated, and its action in conjunction with the other intestinal fluids 

 and in the presence of other alimentary principles in process of digestion. The first 

 definite observations upon these points were made by Bernard. He found that the albu- 

 minoid substances generally, exposed to the action of the pancreatic juice out of the 

 body, became rapidly softened and dissolved in some of their parts, but soon passed into a 

 condition of putrefaction. An analogous change, it will be remembered, also takes place 

 in starchy and fatty matters when exposed to the action of the pancreatic juice out of 

 the body, and they pass through the various stages of transformation respectively into 

 lactic acid and the fatty acids. This putrefactive action does not take place in albuminoids 

 which have been precipitated after having been cooked, or in raw gluten or caseine. The 

 presence of fat also interferes with putrefaction ; so that Bernard concludes that the fats 

 have an important influence in the intestinal digestion of nitrogenized principles. 



Taking into consideration what has been positively ascertained concerning the action 

 of the pancreatic juice upon the albuminoids, there can be no doubt with regard to the 

 importance of its function in the digestion of these principles after they have been ex- 

 posed to the action of the gastric juice. Experiments upon the digestion of these sub- 

 stances after they have passed out of the stomach show that they undergo important and 

 essential changes as they pass down the intestinal canal. While the bile and the intesti- 

 nal juice are by no means inert, they seem to be only auxiliary in their action to the pan- 

 creatic juice. When meat is taken into the stomach or is exposed even for a long period 

 to the action of the gastric juice, there is always more or less insoluble residue, which can 

 be shown by microscopical examination to consist of the muscular substance. 



The preparation which the albuminoids undergo in the stomach is undoubtedly neces- 

 sary to the easy digestion, in the small intestine, of that portion which is not dissolved by 

 the gastric juice. , This fact has been conclusively demonstrated by experiments on in- 

 testinal digestion in the inferior animals and by the observations of Busch in the case of 

 intestinal fistula in the human subject. 



Action of the Bile in Digestion. 



A great deal of diversity of opinion has existed among physiologists concerning the 

 functions of the bile. It is now pretty generally acknowledged that this fluid has, of 

 itself, no marked influence upon any of the different classes of alimentary principles, 

 such as we have observed in the other secretions discharged into the alimentary canal. 

 This being the case, it is important to decide whether the bile be essential in assisting or 

 modifying the action of other secretions or whether it be entirely inert in the digestive 

 process. From the fact that it is poured into the upper part of the small intestine, it 

 would seem that it must have some office, either in modifying the digestion and absorp- 

 tion of food or in the passage of alimentary substances or their residue down the intes- 

 tinal tract. It is difficult to suppose that a fluid which is brought in contact with the ali- 



