THE LIVER. 



177 



character of the liver becomes progressively more masked by the inter- 

 growth of the cell-cords and the large veins. The glandular tissue is subdi- 

 vided by connective tissue into small cylindrical masses, the lobules, which 

 on the surface of the organ are seen as little polygons, 1-2 mm. in diameter. 

 This interlobular tissue is continuous with the fibrous envelope, or capsule, 

 that invests the exterior of the liver, at the transverse fissure being prolonged 

 as the capsule of Glisson into the organ in company with the interlobular 

 vessels. The distinctness with which the lobules are defined depends upon 

 the amount of the interlobular tissue. This is notably abundant in the hog' s 

 liver, in which the lobules appear as sharply marked polygonal areas. In 

 the human liver, on the contrary, the interlobular tissue is very meagre, 

 the lobules, in consequence, being poorly defined and uncertain in outline 

 (Fig. 221). 



The Blood- Vessels of the Lobule. The arrangement of the blood- 

 vessels is the salient feature in the architecture of the fully formed hepatic 



Portal vein 



FIG. 220. Section of liver injected from hepatic vein, showing intralobular capillary network. X 100. 



lobule. The divisions of the portal vein the vessel bringing blood to the liver 

 for its function enter at the transverse fissure and break up into branches 

 which ramify within the interlobular tissue (capsule of Glisson) and encircle 

 the lobules. These interlobular -veins give off numerous small branches that 

 enter the periphery of the lobules to resolve at once into the intralobular 

 capillary network. The general disposition of this network is radial, the 

 capillaries converging towards the middle of the lobule where they join to 

 form and empty into the central or intralobular vein. The course of the 

 latter corresponds with the long axis of the lobule, hence, in cross-sections 

 of the lobule, the central vein appears as a transversely cut channel towards 

 which the capillaries converge (Fig. 220). The capillary network within 

 the lobule is made up of vessels usually about 10 p. in diameter, the widest 

 capillaries (20 /*) being in the immediate vicinity of the afferent and efferent 

 veins. The meshes of the capillary network vary from 15-45 / z m their 

 greatest dimension, those at the periphery being broader and more rounded, 

 while those near the centre of the lobule are narrower and more elongated. 

 12 



