290 A Study of the Structural Unit of the Liver 
eapillary plexus of the lobule. This condition seemed to be true down to 
the largest bile duct. At no time did I find a collecting vein within the 
substance of the liver, and I must, therefore, declare the rami vasculares 
venosi as mythical. 
It is evident by studying good injections of the artery after the portal 
vein has been plugged that the artery communicates with the lobule 
throughout the extent of the vessels of the sixth order and possibly in 
part with those of the fifth order (Fig. 53). All the capillaries in the cap- 
sule of Glisson in this region communicate only with those of the lobule 
and they do not communicate at all with the portal vein. In those regions 
of the liver immediately around portal veins of the fourth order it is 
always found that in their immediate neighborhood there are both ar- 
teries and veins of the sixth order which ramify again, as stated above. 
So down to and including vessels of the fourth order all of the capillaries 
of the artery communicate directly with the capillaries of the lobule. 
By consulting the table giving the number of vessels of the various orders 
it is seen that this observation excludes the possibility of any veins of 
Ferrein arising from oyer a million terminal arteries and leaves them to 
arise from the walls of the main trunks of the first three orders; probably 
there are no more veins of Ferrein that empty into the vena porte than 
can be seen with the naked eye. 
The hepatic artery then supplies the gall bladder and the hilum of the 
liver, and the veins from this region communicate with the portal vein. 
The branches of the artery then enter the lobes of the liver with the 
branches of the portal vein and the bile ducts. Here the artery gives off 
a few branches to the bile duets which form a capillary plexus around 
them, after which it communicates with the capillary plexus of the 
lobule. By far the greater number of arteries enter the centers of the 
portal units and communicate at once with the capillaries; they supply 
the periphery of the lobules. There are about a million of these very 
small terminal arteries, one for each portal unit which then spread out 
toward the nodal points and the hepatic veins. The branches that spread 
over the capsule of the liver supply the subcapsular portal units and then 
communicate with the hepatic veins. Some of the hepatic veins per- 
forate the subperitoneal lobules as described by Kiernan; none of the 
portal twigs reach the surface. The great bulk of the arterial blood 
is equally distributed from the centers of the portal units and is fully 
mixed with portal blood before it reaches the nodal points or the hepatic 
veins. 
