JOLOGY 



the center of each polygonal space presenting a minute aperture, the mouth of an intralobu 

 vein (Fig. 1089). 



Microscopic Appearance (Fig. 1092). Each lobule consists of a mass of cells, hepatic cells, 

 arranged in irregular radiating columns between which are the blood channels (sinusoids). These 

 convey the blood from the circumference to the center of the lobule, and end in the intralobular 

 vein, which runs through its center, to open at its base into one of the sublobular veins. Between 

 the cells are also the minute bile capillaries. Therefore, in the lobule there are all the essentials 

 of a secreting gland; that is to say: (1) cells, by which the secretion is formed; (2) bloodvessels, 

 in close relation with the cells, containing the blood from which the secretion is derived; (3) 

 ducts, by which the secretion, when formed, is carried away. 



1. The hepatic cells are polyhedral in form. They vary in size from 12 to 25," in diameter. 

 They contain one or sometimes two distinct nuclei. The nucleus exhibits an intranuclear net- 

 work and one or two refractile nucleoli. The cells usually contain granules; some of which are 

 protoplasmic, while others consist of glycogen, fat, or an iron compound. In the lower vertebrates, 

 e. g., frog, the cells are arranged in tubes with the bile duct forming the lumen and bloodvessels 

 externally. According to Del6pine, evidences of this arrangement can be found in the human 

 liver. 



2. The Bloodvessels. The blood in the capillary plexus around the liver cells is brought to 

 the liver principally by the portal vein, but also to a certain extent by the hepatic artery. 



The hepatic artery, entering the liver at the porta with the portal vein and hepatic duct, 

 ramifies with these vessels through the portal canals. It gives off vaginal branches, which ramify 

 in the fibrous capsule of Glisson, and appear to be destined chiefly for the nutrition of the coats 

 of the vessels and ducts. It also gives off capsular branches, which reach the surface of the 

 organ, ending in its fibrous coat in stellate plexuses. Finally, it gives off interlobular branches, 

 which form a plexus outside each lobule, to supply the walls of the interlobular veins and the 

 accompanying bile ducts. From this plexus lobular branches enter the lobule and end in the 

 net-work of sinusoids between the cells. 



The portal vein also enters at the porta, and runs through the portal canals (Fig. 1093), 

 enclosed in Glisson's capsule, dividing in its course into branches, which finally break up into a 

 plexus, the interlobular plexus, in the interlobular spaces. These branches receive the vaginal 



and capsular veins, correspond- 



Bile-duct He 'P atic artery i ng to tne vaginal and capsular 



branches of the hepatic artery. 

 Thus it will be seen that all the 

 blood carried to the liver by the 

 portal vein and hepatic artery 

 finds its way into the interlob- 

 ular plexus. From this plexus 

 the blood is carried into the lobule 

 by fine branches which converge 

 from the circumference to the 



Lymphatic 

 vessel 



FIG. 1093. Section across portal canal of pig. X 250. 



FIG. 1094. Bile capillaries of rabbit, 

 shown by Golgi's method. X 450. 



center of the lobule, and are connected by transverse branches (Fig. 1091). The walls of these 

 small vessels are incomplete so that the blood is brought into direct relationship with the liver 

 cells. The lining endothelium consists of irregularly branched, disconnected cells (stellate cells of 

 Kupffer). Moreover, according to Herring and Simpson, minute channels penetrate the liver cells 

 themselves, conveying the constituents of the blood into their substance. It will be seen that the 

 blood capillaries of the liver lobule differ structurally from capillaries elsewhere. Developmentally 

 they are formed by the growth of the columns of liver cells into large blood spaces or sinuses, 

 and hence they have received the name of "sinusoids." Arrived at the center of the lobule, 



