CHAP. XV.] ALIMENTATION. 187 



portal vein.* Secondly, the different parts of the secretory 

 apparatus, the cells, blood-vessels, and ducts, instead of being 

 arranged as elsewhere in distinct tubes or sacs, are closely 

 united and massed together. The secreting cells are collected 

 into small polyhedral or many-sided masses, called hepatic 

 lobules; the blood-vessels form networks around and in the 

 lobules ; while the ducts which carry away the secretion (bile) 

 begin within the lobules in the form of tiny channels, running 

 between the cells. 



FIG. 119. UNDER SURFACE OF LIVER. 1, right lobe; 2, left lobe; 3, 4, 5, smaller 

 lobes; 9, inferior vena cava; 10, gall-bladder; 11, 11, transverse fissure, or "gate of 

 the liver," containing bile duct, hepatic artery, and portal vein. 



The whole liver is invested in an envelope or capsule of con- 

 nective tissue (Glisson's capsule), and the lobules are divided 

 from one another by very delicate partitions of areolar tissue, 

 each lobule being about the size of a pin's head and filled with 

 the special liver cells. 



The large portal vein and the small hepatic artery enter the 

 liver together on its under surface at what is called the " gate 

 of the liver," the bile duct passing out at the same place. The 

 branches of these three vessels, enclosed by loose connective 

 tissue, in which are lymphatics and nerves, accompany one 

 another in their course through the organ. The smallest 

 1 Cf. note on lungs, p. 131. 



