THE LIVER AND THE SECRETION OF BILE 275 



sorbed. It does not pass directly from the biliary ducts into the blood, but is 

 taken up, in part at least, by the lymphatic vessels. If the thoracic duct as well 

 as the bile duct be tied off, it may happen that no constituents of the bile will 

 pass into the blood (Harley) ; but there are statements to the effect that even 

 under these circumstances they may find their way into the general circulation 

 (Wertheimer and Lepage). 



C. THE DISCHARGE OF BILE IN DIGESTION 



When digestion is not going on the secreted bile collects in the gall blad- 

 der; there it loses water and becomes thicker. Neither bodily movements, 

 nor movements of the alimentary canal, fasting, nor appetite have any effect 



FIG. 110. The hourly course of the discharge of bile into the intestine of the dog, following in- 

 gestion of different foods, after Bruno. meat; bread; milk. 



in causing the gall bladder to empty its contents : the bile begins to flow from 

 the bladder into the intestine only at the beginning of digestion. 



The outflow of bile into the intestine is adapted to the immediate require- 

 ments by the following mechanisms. The discharge of bile from the ductus 

 choledochus is controlled by a special sphincter. The gall bladder and the bile 

 duct possess muscles which are under the influence of the splanchnic nerve. It 

 is said that the duodenal sphincter of the ductus choledochus is innervated by 

 the vagus. Phenomena witnessed on stimulation of the splanchnic show fur- 

 ther that the gall bladder, as well as the ductus choledochus and the sphincter, 

 may be reflexly dilated. Again by central stimulation of the vagus, reflex con- 

 traction of the gall bladder and relaxation of the sphincter may be produced. 



The evacuation of the gall bladder and the discharge of bile in digestion, 

 according to Bruno, are elicited by the passage of the stomach contents into the 

 intestine. The substances active in this are the digestive products of proteids, 

 extractives of meat and fats. The carbohydrates evoke no discharge of bile. 

 Since the passage of the stomach contents into the intestine is governed by the 

 kind of food, the discharge of bile is naturally different for different foods, as 

 appears also from the diagram in Fig. 110. 



With respect to the properties of the bile, it should be mentioned that the 

 portions first discharged are thicker than that which comes later, because the 

 former comes from the gall bladder, while the latter is freshly secreted. 



