DIGESTION. 



269 



onul from mutual pressure about -^ to T15 1 j nr inch in diameter, possess- 

 ing one, sometimes two nuclei. The cell-substance contains numerous 

 fatty molecules, and some yellowish-brown granules of bile-pigment. The 

 cells sometimes exhibit slow amoeboid movements. They are held to- 

 gether by a very delicate sustentacular tissue, continuous with the inter- 

 lobular connective tissue. 



To understand the distribution of the blood-vessels in the liver, it 

 will be well to trace, first, the two blood-vessels and the duct which enter 

 the organ on the under surface at the transverse fissure, viz., the portal 

 vein, hepatic artery, and hepatic duct. As before remarked, all three 

 run in company, and their appearance on longitudinal section is shown in 



FIG. 197. 



FIG. 198. 



FIG. 197. A. Liver-cells. B, Ditto, containing various sized particles of fat. 



FIG. 198. Longitudinal section of a portal canal, containing a portal vein, hepatic artery and 

 hepatic duct, from the pig. P, branch of vena portae, situate in a portal canal formed amongst the 

 lobules of the liver, 1 1, and giving off vaginal branches; there are also seen within the large portal 

 vein numerous orifices of the smallest interlobular veins arising directly from it; a, hepatic artery; 

 d, hepatic duct, x 5. (Kiernan.) 



Fig. 198. Running together through the substance of the liver, they are 

 contained in small channels called portal canals, their immediate invest- 

 ment being a sheath of areolar tissue (Glisson's capsule). 



To take the distribution of the portal vein first: In its course through 

 the liver this vessel gives off small branches which divide and subdivide 

 between the lobules surrounding them and limiting them, and from this 

 circumstance called inter-lobular veins. From these small vessels a dense 

 capillary network is prolonged into the substance of the lobule, and this 

 network, gradually gathering itself up, so to speak, into larger vessels, 

 converges finally to a single small vein, occupying the centre of the lobule, 

 and hence called ^ra-lobular. This arrangement is well seen in Fig. 

 199, which represents a transverse section of a lobule. 



