142 PHYSIOLOGY CHAP. 



plexus produces opposite phenomena in the region of the portal 

 vein and in that of the hepatic artery ; while the former contracts 

 with excitation of the plexus, and expands with stimulation of 

 the vagus, the latter contracts on exciting the vagus, and enlarges 

 with excitation of the caeliac plexus. While section of the vagus 

 abolishes the effect of asphyxia on the artery, it does not affect its 

 action on the branches of the portal vein. 



Although the influence of these changes in the tone of the 

 venous and arterial hepatic vessels upon the process of biliary 

 secretion was not studied by the above workers, it may on analogy 

 be taken as highly probable that vascular constriction (particularly 

 of the portal branches) determines a slowing, and dilatation an 

 acceleration, of the flow of bile. 



While there can be no doubt that the secretory activity of the 

 liver, like that of the other glandular organs, is indirectly affected 

 by the nerves which regulate vascular tonicity, there are at 

 present no data to demonstrate the existence of secretory nerves 

 to the liver, exerting a direct control upon the secretion of bile. 

 All the nerves to the liver can be divided without causing arrest 

 of the biliary secretion ; all branches of the nerves to the liver can 

 be excited one after the other, without causing a flow of bile, if 

 the secretion was suspended, or accelerating it if already taking 

 place (Heidenhain). 



Falloise (1903) found on dogs that application of hydrochloric 

 acid to the mucous membrane of the duodenum, or upper part of 

 the small intestine, provoked increase of the biliary secretion. At 

 the same time it may be questioned whether this is a true reflex, 

 as asserted by Fleig. Falloise interprets the phenomenon by 

 admitting the transformation of pro-secretin into secretin, which 

 on reaching the liver increases the formation of bile by local 

 stimulation. In reality this pretended cholagogic action is 

 abolished neither by narcotics, nor by strong doses of atropine. 

 On the other hand, Henri and Portier (1902) observed that the 

 injection of secretin caused an acceleration of biliary secretion. 

 The same objections apply here in regard to the " secretin hypo- 

 thesis " as were raised for the pancreatic and intestinal secretions. 



Friedlander and Barisch (1860) connected the hepatic duct of 

 the guinea-pig with a vertical glass tube, so as to determine the 

 point to which pressure can be raised in the bile ducts. They 

 saw that the bile ascends in the glass tube with a gradually 

 decreasing velocity, which ceases when it has reached a certain 

 height, varying from 184-212 mm. Since the pressure in the 

 portal vein, according to the determinations made by von Basch 

 on dogs, varies from 7-16 mm. Hg, corresponding to a column of 

 bile about 191-208 mm., the pressure under which bile is secreted 

 is always more or less higher than the pressure at which the blood 

 circulates in the portal system. This was confirmed by comparison 



