524 STRUCTURAL ANATOMY OF THE LIVER. 



gives off vaginal branches which form a vaginal hepatic 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 supplies the vasa vasorum of the portal and 

 hepatic veins, and the nutrient 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. 



Physiological and Pathological Deductions. The physiological deduc- 

 tion arising out of this anatomical arrangement is, that the bile is wholly 

 secreted from venous blood, and not from a mixed venous and arterial 

 blood, as stated by Miiller; for although the portal vein receives its blood 

 from two sources, viz. from the chylopoietic viscera and from the capil- 

 laries of the hepatic artery, yet the very fact of the blood of the latter 

 vessel having passed through its capillaries into the portal vein, or in ex- 

 tremely 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 circum- 

 ference. 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 circulation is natural, the colour will be uni- 

 form. But the instant that any cause is developed which shall interfere 

 with the free circulation 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 intralobular veins will become 

 congested, giving rise to a more or less extensive redness in the centre of 

 each of the lobules, while the marginal or non-congested portion presents 

 a distinct border of a yellowish white, yellow, or green colour, according 

 to the quantity and quality of the bile it may contain. " This is 'passive 

 congestion' 9 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 continue, or 

 be from the beginning of a more active kind, the congestion will extend 

 through the lobular venous plexuses "into those branches of the portal 

 vein situated in the interlobular fissures, but not to those in the spaces, 

 which being larger, and giving origin to those in the fissures, are the last 

 to be congested." In this second stage the liver has a mottled appear- 

 ance, the non-congested substance is arranged in isolated, circular, anc 3 

 ramose patches, in the centres of which the spaces and parts of the fissures 

 are seen. This is an extended degree of fiepatic-venous congestion ; it is 



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

 {ia2u:a of Anatomy and Physiology," edited by Dr. Todd. 



