280 A Study of the Structural Unit of the Liver 
or more, passed through the longer and less direct capillaries than 
through the shorter and direct ones. The capillaries passing through 
the nodal puints, therefore, seem to be as well favored as those taking the 
shorter course. In the diagram it is seen that the nodal point is fed 
from three sources, and on account of the great number of capillaries 
in it the resistance to the circulation is probably diminished. It would 
follow that some of the main feeding capillaries should be converted into 
veins, and in growing livers this is the case, but every time a new vein 
is formed, we have a new vascular unit, or a new lobule with two new 
Hic. 46. Arrangement of the capillaries at the nodal point of a lobule. 
x< 85. P, portal vein; h, hepatic vein. 
but smaller nodal points to complicate the situation again. This process 
might be continued until the portal branches communicated with the 
hepatic, were there not some self-regulating force to check it. It appears 
that this force is due to the normal length of the capillary which is about 
4 mm. in the direct course. In the indirect course, 7. e., through the 
nodal points, this distance is about .8 mm., but each nodal point is fed 
from three sides instead of from one, and this arrangement may account 
for this increase in distance without the formation of new veins. 
If the hepatic and portal veins are injected with thick granular 
masses—cinnabar, lamp-black or ultra-marine blue suspended in gelatin— 
