STRUCTURE OF LIVER. 469 



The hepatic artery (h) is divided into two, one for each lobe, and its 

 brunches are surrounded by nerves and lymphatics. 



The vena portce (6) branches, like the artery, into two trunks for the 

 right and left lobes, and gives an offset to the Spigelian lobe; its left 

 branch is the longest. 



Fcetal condition of the umbilical vein. Before birth the previous um- 

 bilical vein occupies the longitudinal fissure, and opens posteriorly into 

 the vena cava; the portion of the vessel behind the transverse fissure re- 

 ceives the name duct us venosus. Branches are supplied from it to both 

 lobes of the liver; and a large one, directed to the right lobe, is continuous 

 with the left piece of the vena portse. Purified or placental blood circu- 

 lates through the vessel at that period. 



Adult state. After birth the part of the umbilical vein in front of the 

 transverse fissure is closed, and becomes eventually the round ligament 

 (fig. 158, c). The ductus venosus is also obliterated, only a thin cord (o?) 

 remaining in its place. Whilst the lateral branches, which are in the 

 same line as, and continuous with the left branch of the vena portae, remain 

 open, and subsequently form part of the left division of the vena portae. 

 Occasionally the ductus venosus is found more or less pervious. 



STRUCTURE OF THE LIVER. The substance of the liver consists of 

 small bodies called lobules or acini; together with vessels which are con- 

 cerned both in the production of the secretion, and in the nutrition of the 

 organ. The whole is surrounded by a fibrous and a serous coat. 



Serous coat. The peritoneum invests the liver almost completely, and 

 adheres closely to the subjacent coat. At certain spots intervals exist be- 

 tween the two, viz., in the fissures occupied by vessels, along the line of 

 attachment of the ligaments, and at the surface touching the gall-bladder. 



The fibrous covering is very thin, but it is rather stronger where the 

 peritoneum is not in contact with it. It invests the liver, and is continu- 

 ous at the transverse fissure with the fibrous sheath (capsule of Glisson) 

 surrounding the vessels in the interior. When the 'membrane is torn from 

 the surface, it will be found connected with fine shreds entering into the 

 liver. 



Size and form of the lobules. The lobules (fig. 161, I) constitute the 

 proper secreting substance, and can be seen either on the exterior of the 

 liver, on a cut surface, or by means of a rent in the mass. As thus ob- 

 served, these bodies are about the size of a pin's head, and measure from 

 ^Lth to -j-^th of an inch in diameter. Closely massed together they pos- 

 sess a dark central point ; and there are indications of lines of separation 

 between them, though they communicate by vessels. By means of trans- 

 verse and vertical sections of the lobules, their form will appear flattened 

 on the exterior, but many sided in the interior of the liver. They are 

 clustered around the smallest divisions of the hepatic vein, to which each 

 is connected by a small twig issuing from the centre, something like the 

 union of the stalk with the body of a small fruit. 



To study the minute structure of the lobules, a microscope will be neces- 

 sary ; and the different vessels of the liver should be minutely injected. 



Constituents of the lobules. Each lobule is composed of minute hepatic 

 cells, which are arranged web-like amongst the ducts and vessels ; and it 

 is provided with a capillary network of vessels, and with a plexus of the 

 bile duct. 



Cells of the lobules. The hepatic or biliary cells (fig. 159, a) form the 

 chief part of the lobule ; they are irregular in form, being rounded or 



