SECRETION. 187 



with a biliary fistula showed that the secretion was ejected in spirts, owing 

 doubtless to contractions of the muscular walls of the larger bile-ducts. But 

 though continuously formed within the liver-cells, the flow of bile is subject 

 to considerable variations. According to most observers the activity of secre- 

 tion is definitely connected with the period of digestion. Somewhere from the 

 third to the fifth hour after the beginning of digestion there is a very marked 

 acceleration of the flow, and a second maximum at a later period, ninth to 

 tenth hour (Hoppe-Seyler), has been observed in dogs. The mechanism con- 

 trolling the accelerated flow during the third to the fifth hour is not perfectly 

 understood. It would seem to be correlated with the digestive changes occur- 

 ring in the intestine, but whether the relationship is of the nature of a reflex 

 nervous act, or whether it depends on increased blood-flow through the organ 

 or upon some action of the absorbed products of secretion remains to be deter- 

 mined. It has been shown that the presence of bile in the blood acts as a 

 stimulus to the liver-cells, and it is highly probable that the absorption of bile 

 from the intestine which occurs during digestion serves to accelerate the secre- 

 tion ; but this circumstance obviously does not account for the marked increase 

 observed in animals with biliary fistulas, since in these cases the bile does not 

 reach the intestine at all. Some imperfect observations by Bidder and Schmidt 

 indicate that the total quantity of bile varies with the character of the food, 

 being larger upon a meat diet than when the subject is fed exclusively upon 

 fats. Exact data as to the effect of the different food-stuffs are lacking. 



Relation of the Secretion of Bile to the Blood-flow in the Liver. 

 Numerous experiments have shown that the quantity of bile formed by the 

 liver varies more or less directly with the quantity of blood flowing through 

 the organ. The liver-cells receive blood from two sources, the portal vein 

 and the hepatic artery. The supply from both these sources is probably essen- 

 tial to the perfectly normal activity of the cells, but it has been shown that bile 

 continues to be formed, for a time at least, when either the portal or the arterial 

 supply is occluded. However, there can be little doubt that the material actually 

 utilized by the liver-cells in the formation of their external and internal secre- 

 tions is brought to them mainly by the portal vein, and that variations in the 

 quantity of this supply influences directly the amount of bile produced. Thus, 

 occlusion of some of the branches of the portal vein diminishes the secretion ; 

 stimulation of the spinal cord diminishes the secretion, since, owing to the large 

 vascular constriction produced thereby in the abdominal viscera, the quantity of 

 blood in the portal circulation is reduced ; section of the spinal cord also dimin- 

 ishes the flow of bile or may even stop it altogether, since the result of such an 

 operation is a general paralysis of vascular tone and a general fall of blood- 

 pressure and velocity ; stimulation of the cut splanchnic nerves diminishes the 

 secretion because of the strong constriction of the blood-vessels of the abdom- 

 inal viscera and the resulting diminution of the quantity of the blood in the 

 portal circulation ; section of the splanchnics alone, however, is said to increase 

 the quantity of bile, in dogs, since in this case the paralysis of vascular tone 

 is localized in the abdominal viscera. The effect of such a local dilatation of 



