1060 



THE ORGANS OF DIGESTION. 



straight vein, which runs through its centre, to open at its base into one oi 

 the radicles of the hepatic vein. Between the cells are also the minute com- 

 mencements of the bile-ducts. Therefore in the lobule we have all the essen- 

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

 formed ; (2) blood-vessels, in close relation with the cells, containing the blood 

 from which the secretion is derived ; and (3) ducts, by which the secretion, 

 when formed, is carried away. Each of these structures will have to be further 

 considered. 



(1) The hepatic cells are of more or less spheroidal form, but may be rounded, 

 flattened, or many-sided from mutual compression. They vary in size from the 

 . A to the ^Qfr of an inch in diameter. They consist of a honeycomb net- 

 work (Klein) without any cell-wall, and contain one or sometimes two distinct 

 nuclei. In the nucleus is a highly refracting nucleolus with granules. Embedded 

 in the honeycomb network are numerous yellow particles, the coloring matter of 

 the bile, and oil-globules. The cells adhere together by their surfaces so as to 

 form rows, which radiate from the centre to the circumference of the lobules. As 

 stated above, they are the chief agents in the secretion of the bile. 



(2) The Blood-vessels. 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. For the sake of clearness the distribution of the 

 blood derived from the hepatic artery may be considered first. 



The hepatic artery, entering the liver at the transverse fissure with the portal 

 vein and hepatic duct, ramifies with these vessels through the portal canals. It 

 gives off vaginal branches which ramify in the capsule of Glisson, and appear to 

 be destined chiefly for the nutrition of the coats of the large vessels, the ducts, 

 and the investing membranes of the liver. It also gives oif capsular branches 

 which reach the surface of the organ, terminating in its fibrous coat in stellate 

 plexuses. Finally it gives off interlobular branches which form a plexus on the 

 outer side of each lobule, to supply its wall and the accompanying bile-ducts. 

 From this, lobular branches enter the lobule and end in the capillary network 

 between the cells. Some anatomists, however, doubt whether it transmits any 

 blood directly to the capillary network. 



FIG 671 Cross section of a lobule of the human liver, showing capillary network between portal and 

 hepatic veins. (Sappey.) 1. Section of intralobular vein. 2, 2. Tributaries from capillary net-work. 3, 3. 

 Interlobular veins from vena portee. 



The portal vein (Fig. 670) also enters at the transverse fissure and run3 

 through the portal canals, enclosed in Glisson's capsule, dividing into branches in 

 its course, which finally break up into a plexus (the interlobular plexus] in the 

 interlobular spaces between the lobules. In their course these branches receive 

 the vaginal and capsular veins, corresponding to the vaginal and capsular 



