STRUCTURE OF THE LIVER. 



199 



. sa 



this condition, the mouth of the ccecum becomes drawn out and narrowed 

 down, and so forms the rudiment of an hepatic duct. 



In man, the liver is the largest gland in the body : it is of a reddish- 

 brown color, dense, and from three to five pounds in weight ; Description of 

 convex on its upper, and concave on its inferior surface. It the liver - 

 has five lobes : the right lobe, the left lobe, the lobus quadratus, the lo- 

 bus spigelii, and lobus caudatus.. It is held in its position by dupli- 

 catures of peritoneum and by a fibrous cord termed its ligaments. Its 

 peritoneal envelope is the cause of its glossy appearance ; its cellular en- 

 velope extends into the interior as sheaths for the vessels. Five classes 

 of vessels are found within it : the branches of the portal vein, those of 

 the hepatic artery, those of the hepatic veins, the lymphatics, and the he- 

 patic ducts ; the latter, converging eventually into a trunk, the hepatic 

 duct, joins with the cystic duct to form the ductus communis choledo- 



chus, which discharges its contents 

 into the duodenum, as seen in Fig. 

 83, in which a is the gall-bladder, 

 which constitutes a temporary recep- 

 tacle for the bile, b the cystic duct, 

 d the hepatic duct, c its branches, e 

 the ductus choledochus, and h its 

 opening into the duodenum. 



The bile-ducts entering the duodenum. The gaU^^der ls Wanting in in- 



vertebrated animals, and first makes its appearance in a rudimentary 

 condition as a dilatation of the bile-duct : it is absent in the horse, pres- 

 ent in the ox ; in the camelopard it was absent in one individual, and 

 the next that happened to be examined had two. 



The intimate structure of the liver in man is, in many particulars, still 

 imperfectly known, though the attention of the most eminent Intimate struc 

 anatomists has been devoted to it. It may, however, be un- ture of the HV- 

 derstood that each hepatic vein, commencing in the substance 

 of the liver, bears upon its capillaries small portions called lobules, from 

 the -J0- to the -fa of an inch in diameter, in a manner which calls to mind 



the arrangement of leaves on a branch, or 

 a bunch of grapes, as represented in Fig. 

 84, a being the vein, #, , , leaf-like lob- 

 ules on its branches. Excluding the lym- 

 phatics, it may be said that four different 

 systems of vessels are engaged in the liver, 

 the portal vein and hepatic artery, the bile- 

 ducts and hepatic veins. The first pair 

 Hepatic veins in the lobules of the liver. are a ff eren t, the second pair efferent ves- 

 sels. The portal vein brings the blood from which bile is to be secre- 



