364 USES OF THE LIVER DUCTLESS GLANDS 



formed. The liver, also, is supplied with both venous and arterial blood, 

 the venous blood largely predominating. In addition it is now recog- 

 nized that the bile is necessary to intestinal digestion, that it contains 

 excrementitious matters and that the cells constantly produce glycogen. 

 The liver produces urea, which is excreted, however, chiefly by the 

 kidneys. It also effects certain important changes in digested and 

 foreign matters that are absorbed from the alimentary canal. 



As regards the bile, the only view that is consistent with actual 

 knowledge is that this secretion is produced by the liver-cells and is 

 taken up by the plexus of canals that surrounds these cells. The 

 little glandular organs attached to the larger branches of the duct secrete 

 mucus that gives the viscidity observed in the bile of some animals. 

 The bile, indeed, is viscid in different animals in proportion to the 

 development of these mucous glands ; and in the rabbit, in which the 

 glands do not exist, the bile has no viscidity. 



Of course the circulation of blood in the liver is a condition neces- 

 sary to the secretion of bile. As regards the question of the production 

 of bile from venous or arterial blood, it has been shown that the mate- 

 rials out of which the bile is formed may be supplied by either the 

 hepatic artery or the portal vein. Bile is secreted after the hepatic 

 artery has been tied, and also after the portal vein has been gradually 

 obliterated, the hepatic artery being intact. Bile is produced in the 

 liver from the blood distributed in its substance by the portal vein and 

 the hepatic artery, and not from the blood of either of these vessels 

 exclusively ; and bile may continue to be secreted, if either one of these 

 vessels is obliterated, provided the supply of blood be sufficient. 



The influence of the nervous system on the secretion of bile has been 

 little studied ; and the question is one of some difficulty and obscurity. 

 The liver is supplied abundantly with nerves, both cerebro-spinal and 

 sympathetic, and some observations have been made on the influence 

 of the nerves on its glycogenic action ; but in regard to the secretion of 

 bile, there is little to be said beyond what has already been stated con- 

 cerning the influence of the nervous system on other secretions. 



The bile is discharged through the hepatic ducts like the secretion 

 of any other gland. During digestion the liquid accumulated in the 

 gall-bladder passes into the ductus communis, in part by contractions 

 of its walls, and in part, probably, by compression exerted by the dis- 

 tended and congested digestive organs adjacent to it. It seems that this 

 secretion which necessarily is produced by the liver without intermis- 

 sion, separating from the blood certain excrementitious matters is re- 

 tained in the gall-bladder for use during digestion. 



Quantity of Bile. The estimates of the daily quantity of bile in the 



