318 FRANKLIN PARADISE JOHNSON 
with the splitting of the lobule two new nodal points are formed, 
and the two new central veins are again found to be directed 
toward these new nodal points. That the hepatic veins do not 
grow into the nodal points and break them into fragments is 
still more evident when it is considered that the terminal cen- 
tral veins are always found within the lobules, while the nodal 
points are always interlobular in position. 
The role of the connective tissue septa in lobule formation. In 
order to understand clearly the rdle played by the connective- 
tissue septum in the splitting of one hepatic lobule into two, it 
will be necessary to review in their proper sequence the events 
which take place in the formation of new lobules. The first 
unmistakable evidence of splitting in a lobule is the formation 
of an additional branch of the hepatic vein, either by the bifurea- 
tion of a terminal vein or by its outward growth from the side of 
an existing vein. At the same time, however, new branches of 
the portal vein are similarly forming, although these latter 
branches are not indicative of the formation of new lobules. 
Next follows the beginning of the cleavage, which consists at first 
of the parallel arrangement of liver cells and is afterward followed 
by an ingrowth of connective tissue. The growth of the new 
branches of the portal vein takes place along the fissures of the 
new septum, if they have not preceded it (fig. 26). The new 
septum comes to possess in this way a new nodal point. Branches 
of the portal vein, however, do not actually enter the new septum 
to break up its nodal point until both new lobules are fully 
formed, and not until the new lobules have increased sufficiently 
in size to warrant this addition to the vascular system. 
It is evident, therefore, that the real and essential phase of 
lobule formation is that concerned with the vascular system. 
New lobules are actually in existence when certain relations be- 
tween the new branches of the portal veins and those of the he- 
patic veins become established. The new branches of the veins 
determine the position of the new septa, just as they do shortly 
before birth when the first evidences of dividing septa appear. In 
the early stages, before traces of the septa are at all apparent, 
similar branches of both systems of veins are formed, establish- 
