418 THE SOLIDS. 



of; and it is the capillaries of both hepatic and portal veins, 

 thus united, that constitute the lobular capillary plexus, 

 (Plate LV.^. 4.; Plate Irfl.fig. 1.) 



The lobular plexus may be completely injected either from 

 the portal or hepatic veins, as might be supposed from the 

 fact of its being constituted of vessels derived from both. 

 This plexus, however, is not always fully injected : it is 

 only when the operation of injection has been very success- 

 fully performed that this result is secured : sometimes, in 

 injecting from the portal vein, the injection fills only those 

 vessels which ramify on the surface of the lobules, viz. the in- 

 terlobular veins, as represented in Plate ILV.Jig. 4. ; in other 

 instances, the injection will penetrate further, and fill that 

 portion of the lobular plexus which is formed by the capil- 

 laries which belong especially to the portal vein ; in this case 

 a zone of capillaries surrounds each lobule, as figured in 

 Plate LVI. fig. 1. In others, again, the injection will fill 

 the entire lobular plexus, and extend even to the central 

 lobular hepatic vein (Plate LVI. fig. 4) ; in this latter case, 

 the entire section of the liver appears but a mass of capillaries, 

 the size and form of the lobules being indicated merely by 

 the cut extremities of the larger lobular and interlobular 

 vessels. 



On the other hand, in injecting from the hepatic veins, the 

 injection may reach only the central lobular vein and its 

 principal ramifications, as shown in Plate LV.^. 1. ; or it 

 may fill that portion of the lobular plexus especially formed 

 by the capillaries of the hepatic veins, in which case each 

 lobule will appear to be the centre of a separate injection 

 (Plate LV.^. 2.) ; lastly, the entire lobular capillary plexus 

 is sometimes injected from the hepatic veins in the same 

 manner as from the portal vein. 



In those instances in which two lobules are seen to be 

 united together, the vessels are also observed to proceed 

 directly from one to the other ; this communication is es- 

 pecially evident in injections of the hepatic veins. (Plate L Y. 



fig- 2-) 



The form of the portal vein, from its origin in the villi of 



