406 



THE DIGESTIVE SYSTEM 



blood-vessels and hepatic ducts this fissure serving as a hilum for the 

 organ. The liver is very irregular in outline and shape, and comprises 

 five so-called lobes of very unequal size. In the adult its weight is 



Central vein 



FIG. 379. DIAGRAM OF LIVER LOBULES, THE UPPER Two Cur TRANSVERSELY, 

 THE LOWER LONGITUDINALLY. 



The portal veins are blue striped; the hepatic veins (central with branches, and 

 sublobular) are solid blue; the hepatic arteries are red; and the bile canals black. 

 (After Merkel.) Cells not indicated. 



about one-fortieth that of the body, aboiit 3 to 3% pounds. The 

 parenchyma of the organ arises from a tubular outgrowth of the embry- 

 onic duodenum, hence entodermal ; the interstitial tissue develops in 

 part from the meseuchyma of the caudal layer of the primitive dia- 



