326 FRANKLIN PARADISE JOHNSON 
layers, into the reticulum between which collagen fibrils push 
from the surface of the lobule. In the case of 1) the septum com- 
pletes itself gradually in the plane of the old central vein, which, 
when the septum is complete, becomes a sublobular vein. Usu- 
ally before the septum is fully completed the newly formed 
lobules show evidences of further segmentation. 
4. The growth of the portal veins takes place by an increase in 
length and by the formation of new branches which spread them- 
selves between the lobules. They grow into the nodal points 
and split them up into additional ones. 
5. The central veins grow by an increase in length and by the 
formation of new branches which are always intralobular in posi- 
tion. They are directed and grow toward certain nodal points, 
but never reach them. . 
6. In their growth both the terminal hepatic and portal veins 
never approach nearer one another than one-half the diameter of 
the lobules, as pointed out by Mall. 
7. The connective tissue septa of the pig’s liver play only a 
passive role in the formation of new lobules. They grow in 
between the new lobules after they have really formed. 
8. The growth of the liver takes place throughout all stages, 
1) by an increase in the number of its lobules; 2) by an increase 
in size of its lobules. 
9. The growth of the lobules likewise takes place, 1) by an in- 
crease in the numbers of its hepatic cells and sinusoids; 2) by an 
increase in the size of the hepatic cells. The latter is counter- 
balanced to a certain degree by a decrease in the diameters of 
the sinusoids. 
10. In general, all parts of the liver grow simultaneously and 
equally. There is a constant shifting of lobules peripherally, 
but this takes place in such a way as to produce a minimum 
amount of change in the relation of one lobule to another. 
11. It is probable that the lengthening of lobules in their 
growth (not an equal swelling in all directions) produces local 
disturbances which manifest themselves by giving rise to the 
great variety in shapes of the lobules. 
