300 A Study of the Structural Unit of the Liver 
the liver cells have all been destroyed ; then the epithelial cells of the gall 
ducts take upon themselves the more complicated process of regeneration 
of liver tissue. At any rate, it is now well known that liver cells often 
contain more than one nucleus and that in a variety of pathological dis- 
turbances as well as in normal development the bile ducts have a tremen- 
dous power of growth. The aberrant bile ducts have been known since 
the time of Ferrein, and probably represent liver tissue which was present 
and active at some earlier stage of development.” 
It has been proved quite conclusively by Toldt and Zuckerkand1 in their 
excellent study on the growth of the liver that degeneration takes place 
in one part of the organ while it is growing large in another portion. 
The vasa aberrantia mark those portions which have degenerated as 
along the left lateral ligament and the region of the vena cava and 
the gall bladder. For example, the gall bladder in its growth encroaches 
upon the substance of the liver and causes its atrophy. The liver lobule 
in degenerating is often reduced to small islands which have the portal 
vein on one side of them and the hepatic on the other, returning to its 
early embryonic state. It is probable that a similar but diffuse degen- 
eration is taking place in many portions of the growing liver, for vessels 
which are of equal size in a given step are often found very unequal sub- 
sequently. It is also known that pressure by foreign bodies, by exostoses 
and by the ribs in excessive lacing may produce atrophy of the liver which 
is always marked by aberrant bile ducts, with hypertrophy elsewhere in 
the organ. 
The striking experiments of Ponfick first showed us to what extent 
the liver may regenerate. His valuable communication also illustrates 
most beautifully that liver lobules do not hypertrophy, but sprout and 
give rise to new lobules, a conclusion which he thinks he disproves. Pon- 
fick finds that after a portion of the liver has been removed the lobules 
in the remaining portion coalesce, and are not sharply defined as they 
should be in their hypertrophy (p. 86). He repeatedly states that it is 
difficult to find enlarged lobules, but in their stead he finds heart-shaped 
or clover-leaf-shaped lobules (pp. 104, 107), exactly what is to be ex- 
pected in a growing liver. However, he does state that when the liver 
hypertrophies evenly in all directions the circumferences of the lobules 
are increased, two, three, or even four, times. This statement he illus- 
trates with a figure of a lobule (Fig. 2) which is compound and on ac- 
count of the large veins in it must be from its base, a condition which 
may be found in any liver which is not growing. His figure 7 which is 
2 Toldt and Zuckerkandl, Sitzungsber. d. Wiener Akademie, LXXII, 1876. 
