384 A MANUAL OF PHYSIOLOGY 



the fistula. A circulation of a smaller proportion of the bile- 

 pigments is also probable, but there is no circulation of the biliary 

 cholesterin (Stadelmann). 



Of the direct influence of nerves, either on the secretion of bile or 

 on its expulsion, we have scarcely any knowledge, scarcely even any 

 guess which is worth mentioning here. It is true the secretion of 

 bile may be distinctly affected by the section and stimulation of 

 nerves which control the blood-supply of the stomach, intestines, 

 and spleen, for the quantity of blood passing by the portal vein to 

 the liver depends upon the quantity passing through these organs, 

 and the rate of secretion is diminished when the blood-supply is 

 greatly lessened." In this way stimulation of the medulla oblongata, 

 the spinal cord, or the splanchnic nerves stops or slows the secre- 

 tion of bile by constricting the abdominal vessels ; and the same 

 effect can be reflexly produced by the excitation of afferent nerves. 



The right splanchnic nerve contains inhibitory with some motor 

 fibres, and the vagi (especially the left) contain motor fibres for 

 the gall-bladder. Probably its contraction takes place naturally 

 in response to reflex impulses from the mucous membrane of the 

 duodenum, for the application of dilute acid to the mouth of the 

 bile-duct causes a sudden flow of bile,* and the acid contents of the 

 stomach, when projected through the pylorus into the intestine, 

 have a similar effect. But, in addition, as we have seen, the 

 secretin formed will cause an increase in the rate of secretion of the 

 bile. In studying the effect of secretin it is necessary to obtain 

 it free from bile-salts, since these cause of themselves an increased 

 secretion of bile. When this is done by dissolving out with 

 alcohol any bile-salts which may be present in the extract of 

 intestinal mucous membrane, a solution of the residue containing 

 the secretin still evokes a rapid secretion of bile. The fact that 

 the same hormone excites the formation both of pancreatic 

 juice and bile is obviously related to that common action of 

 the two juices in digestion on which we have already dwelt. 



When food passes into the stomach, there is at once a sharp 

 rise in the rate of secretion of bile. A maximum is reached 

 from the fourth to the eighth hour that is, while the food is 

 in the intestine. There is then a fall, succeeded by a second 

 smaller rise about the fifteenth or sixteenth hour, from which 

 the secretion gradually declines to its minimum. Upon the whole, 

 the curves of secretion of pancreatic juice and bile show a fairly 

 close correspondence, except that the latter is more nearly con- 

 tinuous. But when we compare the curves representing the rate 

 at which the bile actually enters the intestine with the curve of 

 pancreatic secretion (Fig. 152), we are struck by their almost 

 absolute parallelism. This lends additional support to the con- 



* This result seems to be difficult to realise experimentally. Bain- 

 bridge and Dale could not elicit reflex contraction of the gall-bladder (in 

 anaesthetized animals) in this way. 



