STRUCTURE OF THE LIVER. 515 



will be observed that the quadrilateral interval, in front of the trans- 

 verse bar, represents the lobus quadratus; the triangular space 

 behind the bar, represents the Spigelii ; and the apex of the letter, 

 the point of union between the inferior vena cava, and the remains 

 of the ductus venosus. 



The Vessels entering into the structure of the liver are tdsofive in 

 number ; they are, the 



Hepatic artery, 

 Portal vein, 

 Hepatic veins, 

 Hepatic ducts, 

 Lymphatics. 



The Hepatic artery, portal vein, and hepatic duct enter the liver 

 at the transverse fissure, and ramify through portal canals to every 

 part of the organ ; so that their general direction is from below 

 upwards, and from the centre towards the circumference. 



The Hepatic veins commence at the circumference and proceed 

 from before backwards, to open into the vena cava, on the posterior 

 border of the liver. Hence the branches of the two veins cross each 

 other in their course. 



The portal vein, hepatic artery, and duct are moreover enveloped 

 in a loose cellular tissue, the capsule of Glisson, which permits them 

 to contract upon themselves when emptied of their contents; the 

 hepatic veins, on the contrary, are closely adherent by their parietes 

 to the surface of the canals in which they run, and are unable to 

 contract. By these characters the anatomist is enabled, in any sec- 

 tion of the liver, to distinguish at once the most minute branch of 

 the portal vein from the hepatic vein ; the former will be found more 

 or less collapsed, and always accompanied by an artery and duct, 

 and the latter widely open and solitary. 



The Lymphatics are described in the Chapter dedicated to those 

 vessels. 



The Nerves of the liver are derived from the systems both of 

 animal and of organic life; the former proceed from the right 

 phrenic and pneumogastric nerves, and the latter from the hepatic 

 plexus. 



Structure and Minute Anatomy of the Liver, according to Mr. 



Kiernan. 



The Liver is composed of lobules, of a connecting medium, called 

 Glisson 's capsule, of the ramifications of \\\eportal vein, hepatic duct, 

 hepatic artery, hepatic veins, lymphatics, and nerves, and is enclosed 

 and retained in its proper situation by the peritoneum. I shall 

 describe each of these structures singly, following rigidly the dis- 

 coveries of Mr. Kiernan. 



