362 EXCRETION OF BILE. 



This occurs (1.) Owing to the continual pressure of the newly- 

 formed bile within the interlobular bile-ducts forcing onward the bile 

 in the excretory ducts. 



(2.) Owing to the interrupted periodic compression of the liver from 

 above, by the diaphragm, at every inspiration. Farther, every inspira- 

 tion assists the flow of blood in the hepatic veins, and every respiratory 

 increase of pressure within the abdomen favours the current in the 

 portal vein. 



It is probable that the diminution of the secretion of bile, which occurs after 

 bilateral division of the vagi, is to be explained in this way; stilt it is to be 

 remembered, that the vagus sends branches to the hepatic plexus. It is not decided 

 whether the biliary excretion is diminished after section of the phrenic nerves and 

 paralysis of the abdominal muscles. 



(3.) Owing to the contraction of the smooth muscles of the larger bile- 

 ducts and the gall-bladder. Stimulation of the spinal cord, from which 

 the motor nerves for these structures pass, causes acceleration of the 

 outflow, which is afterwards followed by a diminished outflow (Heiden- 

 hain, J. Munk). Under normal conditions, this stimulation seems to 

 occur reflexly, and is caused by the passage of the ingesta into the 

 duodenum, which, at the same time, excites movement of this part of 

 the intestine. 



(4.) Direct stimulation of the liver (Pfliiger), and reflex stimulation 

 of the spinal cord (Rohrig), diminish the excretion ; while extirpation 

 of the hepatic plexus (Pfliiger), and injury to the floor of the fourth 

 ventricle (Heidenhain) do not exert any disturbing influence. 

 (5.) A relatively small amount of resistance causes bile to stagnate 

 in the bile-ducts. 



A manometer, tied into the gall-bladder of a guinea-pig, supports a column of 

 200 millimetres of water; and secretion can take place under this pressure 

 (Heidenhain, Friedlander, Barisch). If this pressure be increased, or too long 

 sustained, the watery bile passes from the liver into the blood, even to the amount 

 of four times the weight of the liver, thus causing solution of the red blood- 

 corpuscles by the absorbed bile ; and very soon thereafter, haemoglobin appears in 

 the urine. 



180. Reabsorption of Bile. 



Phenomena of Jaundice (Icterus; Cholaemia). 



Absorption Jaundice. When an impediment or resistance is offered to the 

 outflow of bile into the intestine e.g., by a plug of mucus, or a gall-stone 

 which occludes the bile-duct, or where a tumour or pressure from without, makes it 

 impervious the bile-ducts become filled with bile and cause an enlargement of the 

 liver. The pressure within the bile-ducts is increased. As soon as the pressure 

 has reached a certain amount, which it soon does when the bile-duct is occluded 

 (in the dog 275 mm. of a column of bile Afanassiew) reabsorption of bile from 

 the distended larger bile-ducts takes place into the lymphatics (not the blood- 



