Ts of the Human Liver. ee 
After having entered the lobules, both the branches of the vein and 
artery send off their ultimate ramuscules from which the capillaries 
of the blood arise. Thus the portal vein and hepatic artery finally 
join each other in a common capillary network (Fig. 1). The 
termination of this network takes place in the smaller branches of 
the hepatic veins, which were named by “ Kiernan,” “the imtra- 
lobular hepatic veins.” By the union of these, larger branches are 
formed, which have been termed the “inter-lobular hepatic veins,” 
from the fact that they run between the lobules. 
These, in their turn, unite to form still larger branches, until, 
by repeated junctions, the larger trunks of the hepatic ves are 
formed. Those venules, however, coming from lobules, adjacent to 
the various trunks, empty directly into them, without passing first 
through a series of increasing vessels. Thus, I have observed small 
hepatic venules, s}5 of an inch in diameter, empty into the largest 
hepatic venous trunks. 
In the human liver, it is difficult to define the exact termination 
of the “inter-lobular” and the commencement of the “intra- 
lobular” vessels by their diameter or length. The best way of 
distinction would be to call them “ intra-lobular ” as long as they 
continue to receive the capillaries of the parenchyma, and “ inter- 
lobular ” when they have ceased to do so. 
The average diameter of the inter-lobular hepatic veins is about 
7s of aninch. Their course through the parenchyma of the organ 
is straight. The intra-lobular veins arise almost at right or slightly 
acute angles from them, and have a diameter of 235 to gdp of an 
inch. I have, however, seen some branches, 74> of an inch in 
diameter, still receiving capillary vessels. The intra-lobular hepatic 
veins mostly terminate in a bifurcation, the branches of which have 
a diameter from yoo to 4250 of an inch; but frequently, before 
terminating, other very short branches are seen arismg from them 
at right angles. 
It has already been mentioned that the larger trunks of the 
hepatic veins run almost at right angles with those of the portal 
vein and hepatic artery, and that the branches resulting from the 
first subdivisions of these vessels next assume a course almost 
parallel to each other, and, at the same time, radiating throughout 
the organ. The finer branches, however, cross each other again at 
right angles like the original trunks from which they descended. 
Structure.—After the capsule is removed from the portal veins, 
their walls consist only of two coats. The outer one is thick but 
of a loose texture, composed of very coarse bundles of fibrous tissue 
intermixed with the elastic element; the inner one is a thin and 
dense fibrous membrane, lined by an epithelium, constituting the 
serous coat of the vessel. The cells of the epithelium are hexa- 
gonal, containmg a round or oval nucleus with granules; their 
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