272 EXCRETION OF BILE. 



liver-cells, which are always in a greater or less degree of activity ; (2) the bile- 

 expelling mechanism, which is specially active at certain periods of digestion 

 ( 178)]. 



Excretion of bile is due to (1) the continual pressure of the newly-formed 

 bile within the interlobular bile-ducts forcing onward the bile in the excretory 

 ducts. 



(2) The interrupted periodic compression of the liver from above, by the 

 diaphragm, at every inspiration. Further, every inspiration 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 ; still 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) 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. 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, and reflex stimulation of the spinal cord, 

 diminish the excretion ; while extirpation of the hepatic plexus and injury to the 

 floor of the fourth ventricle do not exert any disturbing influence. 



(5) A relatively small amount of resistance causes bile to stagnate in the bile- 

 ducts. 



Secretion Pressure. 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. 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. [This fact is of practical importance, as duodenitis may give rise to symptoms of 

 jaundice, the resistance of the inflamed mucous membrane being sufficient to arrest the out- 

 flow of bile. ] 



Passage of Substances into the Bile. Some substances which enter the blood pass into the 

 bile ; especially the metals, copper, arsenic, iron, &c. ; potassium iodide, bromide, and 

 sulphocyanide, and turpentine ; to a less degree, cane-sugar and grape-sugar ; sodium salicylate, 

 and carbolic acid. If a large amount of water be injected into the blood, the bile becomes 

 albuminous ; mercuric and mercurous chlorides cause an increase of the water of the bile. 

 Sugar has been found in the bile in diabetes ; leucin and tyrosin in typhus, lactic acid and 

 albumin in other pathological conditions of this fluid. 



180. REABSOEPTION OF BILE; JAUNDICE. I. Absorption-Jaundice. When resist- 

 ance 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), 

 reabsorption of bile from the distended larger bile-ducts takes place into the lymphatics (not 

 the blood-vessels) of the liver, the bile-acids pass into the lymphatics of the liver. [The 

 lymphatics can be seen at the portal fissure filled with yellow-coloured lymph.] The lymph 

 passes into the thoracic duct, and so into the blood (Fleischl). Even when the pressure is very 

 low within the portal vein, bile may pass into the blood without any obstruction to the bile-duct 

 being present. This is the case in Icterus neonatorum, as after ligature of the umbilical cord 

 no more blood passes through the umbilical vein ; further, in the icterus of hunger, "hunger- 

 jaundice " as the portal vein is relatively empty, owing to the feeble absorption from the 

 intestinal canal (CI. Bernard). 



II. Cholsemia may also occur, owing to the excessive production of bile (hypercholia), the 

 bile not being all excreted into the intestine, so that part of it is reabsorbed. This takes 

 place when there is solution of a great number of blood- corpuscles ( 178, 6), which yield 

 material for the formation of bile. Thick inspissated bile accumulates in the bile-ducts, so that 

 stagnation, with subsequent reabsorption of the bile, takes place. The transfusion of hetero- 



