324 FRANKLIN PARADISE JOHNSON 
These points concerning the growth of the liver can best be 
exemplified by the following diagrams. In figure 20, let the circle 
A represent a circumscribed mass of liver tissue surrounding a 
large vein of either the hepatic or portal systems. The zones B 
and C represent concentric zones of liver substance about A. 
When A increases in size (fig. 21), it might at first seem that it 
would press against the zone B and this in turn against C, tend- 
ing to produce changes in them. But the zones B and C are 
likewise growing at the same rate as A. In their growth they 
expand just as metal rings expand when they are heated. The 
20 21 
Figs. 20 and 21 Diagrams to show manner of growth of liver as a whole. 
fact that the center is filled by A alters in no way the shape the 
zone B will assume. The expansion of C similarly makes room 
for B. The process is exactly similar to that which takes place 
in the expansion of any solid ball of metal when heated evenly. 
A lobule in figure 21 at the point m would be further away from 
both center and periphery than at its former point m in figure 20. 
Similarly, the vein increases in length as the liver expands. Its 
increase is due in part to the growth at the tips of its branches 
and in part to an increase in length of its trunk. 
The above hypothesis explains in a general way the growth 
of the liver and is based on the assumption that the liver tissue 
