580 STRUCTURAL ANATOMY OF THE LIVER. 



amined and contrasted with an injected lobule, it will be found that 

 the acini of Malpighi in the former are identical with the injected 

 lobular biliary plexus in the latter, and the blood vessels in both will 

 be easily distinguished from the ducts."* 



Glisson's capsule is the areolar tissue which envelopes the hepatic 

 artery, portal vein, and hepatic duct, during their passage through 

 the right border of the lesser omentum, and which continues to sur- 

 round them to their ultimate distribution in the substance of the 

 lobules. It forms for each lobule a distinct capsule, which invests it 

 on all sides with the exception of its base, connects all the lobules 

 together, and constitutes the proper capsule of the entire organ. But 

 Glisson's capsule is not mere areolar tissue ; " it is to the liver what 

 the pia mater is to the brain ; it is a cellulo- vascular membrane, in which 

 the vessels divide and subdivide to an extreme degree of minuteness ; 

 which lines the portal canals, forming sheaths for the larger vessels 

 contained in them, and a web in which the smaller vessels ramify ; 

 which enters the interlobular fissures, and with the vessels forms the 

 capsules of the lobules ; and which finally enters the lobules, and with 

 the blood-vessels expands itself over the secreting bilary ducts." Hence 

 arises a natural division of the capsule into three portions, a vaginal, 

 an interlobular, and a lobular portion. 



The vaginal portion is that which invests the hepatic artery, 

 hepatic duct, and portal vein, in the portal canals ; in the larger canals 

 it completely surrounds these vessels, but in the smaller is situated 

 only on that side which is occupied by the artery and duct. The in- 

 terlobular portion occupies the interlobular fissures and spaces, and the 

 lobular portion forms the supporting tissue to the substance of the 

 lobules. 



The Portal vein, entering the liver at the transverse fissure, ramifies 

 through its structure in canals, which resemble, by their surfaces, the 

 external superficies of the liver, and are formed by the capsular sur- 

 faces of the lobules. These are the portal canals, and contain, besides 

 the portal vein with its ramifications, the artery and duct with their 

 branches. 



In the larger canals, the vessels are separated from the parietes of 

 the cavity by a web of Glisson's capsule ; but, in the smaller, the 

 portal vein is in contact with the surface of the canal for about two- 

 thirds of its cylinder, the opposite third being in relation with the 

 artery and duct and their investing capsule. If, therefore, the portal 

 vein were laid open by a longitudinal incision in one of these smaller 

 canals, the coats being transparent, the outline of the lobules, bounded 

 by their interlobular fissures, would be as distinctly seen as upon the 

 external surface of the liver, and the smaller venous branches would 

 be observed entering the interlobular spaces. 



The branches of the portal vein are, the vaginal, interlobular, and 



* The Anatomy and Physiology of the Liver, by Mr. Kiernan, Phil. Trans. 

 1 833, from which this, and the other paragraphs within inverted commas, on 

 the structure of the liver, are quoted. 



