322 FRANKLIN PARADISE JOHNSON 
that ‘‘the multiplication of lobules continues long after birth, 
and partly divided, compound forms were recognized in the adult 
by Kiernan.”’ At just what time lobule formation is fully com- 
pleted I have not determined; there are some evidences that a few 
lobules are undergoing division in the so-called ‘adult’ stages I 
have studied. 
In studying the growth of a solid mass of tissue such as the 
liver, we must consider the possibility of both peripheral and cen- 
tral growth; in the former the increase takes place by a laying 
down of successive layers on the surface; in the latter the growth 
takes place by an increase in the size and number of the units 
within the organ. The growth of the liver may be described as 
TABLE 2 
ESTIMATED 
SIZE OF DIAMETER NUMBER OF 
STAGE HEPATIC CELLS |OF SINUSOIDS IN|CELLS IN AVER- 
IN MICRA MICRA AGED-SIZED 
LOBULE 
CO: natal yi ee RRRSIS S! . 250d EL I0. HOYER. 13.9 22.9 
152 mms. MEER CM Se ee 12.5 13.6 
Beds riipy. HAAS: ee Se aie, vee 16.0! 8.0 21,000 
4cweekstoldiy Hk, AIRE SAS Lk, Ly 7/ 9.8 79,000 
2 month sioladwain |. nes ns eyes y. Mis es 13.1 12.1 97,900 
Alult.e SPO eee eee: be. ue se 19.8 8.0 465,000 
1 The cells in this stage were unusually large and vesicular. 
central, that is, taking place more or less evenly throughout. 
After a study of sections of developing livers, I was at first led 
to believe that mitosis proceeded somewhat more rapidly in the 
surface lobules than in the deeper seated ones (718 b) but the 
further study of this point does not confirm this view. Mitotic 
figures even in favorable sections of well-preserved livers are not 
abundant,! making it extremely difficult to note any actual varia- 
tion in their distribution. I am inclined to believe that in general 
all parts of the liver are growing at the same rate, since the liver 
1 Tlling (’05), who has studied the liver cells of growing and adult animals, 
states: ‘‘In hiesigen Institute (Tierarztlichen Hochschule zu Dresden) sind im 
Laufe der Jahre Tausende von Leberpriparaten von allen Haustieren unter- 
sucht, aber niemals mitotische Kernfiguren gefunden worden.”’ 
