STRUCTURAL ANATOMY OP THE LIVER. 521 



plexus, from which the interlobular branches arise, and these latter 

 terminate ultimately in the lobular venous plexuses of the portal 

 vein. The artery ramifies abundantly in the coats of the hepatic 

 ducts, enabling them to provide their mucous secretion ; and sup- 

 plies the vasa vasorum of the portal and hepatic veins, and the nu- 

 trient vessels of the entire organ. 



The Hepatic veins commence in the centre of each lobule by 

 minute radicles, which collect the impure blood from the lobular 

 venous plexus and convey it into the intralobular veins; these open 

 into the sublobular veins, and the sublobular veins unite to form the 

 large hepatic trunks by which the blood is conveyed into the vena 

 cava. 



The physiological deduction arising out of this anatomical ar- 

 rangement is, that the bile is wholly secreted from venous blood, and 

 not from a mixed venous and arterial blood, as is believed by 

 Miiller ; for although the portal vein receives its blood from two 

 sou%es, viz. from the chylopoietic viscera and from the capillaries 

 of the hepatic artery, yet the very fact of the blood of the latter ves- 

 sel having passed through its capillaries into the portal vein, or in 

 extremely small quantity into the capillary network of the lobular 

 venous plexus, is sufficient to establish its venous character.* 



The pathological deductions depend upon the following facts : 

 Each lobule is a perfect gland ; of uniform structure, of uniform 

 colour, and possessing the same degree of vascularity throughout. 

 It is the seat of a double venous circulation, the vessels of the one 

 (hepatic) being situated in the centre of the lobule, and those of the 

 other (portal) in the circumference. Now the colour of the lobule, 

 as of the entire liver, depends chiefly upon the proportion of blood 

 contained within these two sets of vessels ; and so long as the cir- 

 culation is natural the colour will be uniform. But the instant that 

 any cause is developed which shall interfere with the free circula- 

 tion of either, there will be an immediate diversity in the colour of 

 the lobule. 



Thus, if there be any impediment to the free circulation of the 

 venous blood through the heart or lungs, the circulation in the 

 hepatic veins will be retarded, and the sublobular and the intra- 

 lobular veins will become congested, giving rise to a more or less 

 extensive redness in the centre of each of the lobules, while the mar- 

 ginal or non-congested portion presents a distinct border of a yel- 

 lowish white, yellow, or green colour, according to the quantity 

 and quality of the bile it may contain. " This is ' passive congestion 1 

 of the liver, the usual and natural state of the organ after death ;" 

 and, as it commences with the hepatic vein, it may be called the 

 first stage of hepatic-venous congestion. 



But if the causes which produced this state of congestion con- 

 tinue, or be from the beginning of a more active kind, the conges- 



* For arguments upon this contested question, see the article " Liver," in the " Cyclo- 

 pedia of Anatomy and Physiology," edited by Dr. Todd. 



G6 



