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 



ictiL 



_rT~ a \.Porfa! 



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, about 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 iri 

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



