THE LIVER 161 



drained away by the hepatic veins. The plan of structure of 

 the liver is best understood when viewed with reference to 

 the hepatic veins. These, if traced backwards, are found 

 to break up into fairly straight vessels, each of which has 

 a large number of lateral branches. Each of the lateral 

 branches is in the centre of a mass of cells, which are packed 

 round it in radiating columns. These masses, which have a, 

 diameter of from 1 to 2 millimetres, are termed " lobules." 

 By mutual pressure the lobules are squeezed into a pentagonal 

 or hexagonal form. The vein in the centre of the lobule is the 

 intralobular vein. Turn now to the portal vein ; this is seen 

 to break up into branches which run between the lobules, 

 and are therefore termed " interlobular veins." The branches 

 of the hepatic artery also run between the lobules, as do the 

 radicles of the bile-duct. Each lobule is a liver in miniature. 

 The blood of the portal vein, which has come from the spleen, 

 in which red blood-corpuscles are destroyed, and from the 

 stomach and intestines, from which it has absorbed the pro- 

 ducts of digestion, is poured over the surface of the lobule, to 

 be filtered through into its central intralobular vein. In its 

 passage from the interlobular veins (and branches of the hepatic 

 artery) to the intralobular vein the blood is confined to radiating 

 capillary channels ; but since these merely prevent the escape of 

 red blood-corpuscles without imposing any restrictions upon 

 the exudation of blood- plasma, the portal blood is to all intents 

 and purposes filtered through the columns of liver-cells. The 

 body-substance of the liver-cells is soft, destitute of envelope, 

 and capable, when free on the (warmed) stage of a microscope, 

 of changing in form, somewhat after the manner of a leucocyte. 

 Such cells have a great capacity for taking up the products 

 of digestion. Possibly they take up and store fats and pro- 

 teins, but undoubtedly it is their chief business to absorb 

 sugar which accumulates as glycogen in their substance. 

 The glycogen is handed out to the hepatic blood as required. 

 The pigment which results from the disintegration of red 

 blood-corpuscles in the spleen is secreted, along with the bile- 

 salts, into minute channels, or canaliculi, which groove the flat 

 surfaces of adjacent liver-cells. These canaliculi converge to 

 the bile-ducts. The liver is therefore at the same time the 

 storehouse of sugar which it takes up from the blood when 



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