DEVELOPMENT OF LOBULE OF PIG’S LIVER 303 
however, has been abundantly proved by the researches of Van 
der Stricht (’91); Kostanecki (92), Engel (99), Lobenhoffer 
(08), and others. Large mononuclear giant-cells, also de- 
scribed by Kdlliker, are to be found sparsely scattered through 
sections of the liver. In the later fetal stages both the group 
of embryonic blood-cells and the giant-cells become fewer and 
fewer, as is agreed by all investigators. I find with Theopold, 
however, that they have not all disappeared at birth and that 
a few may be found for several weeks after birth. 
The first indication of a segmentation of the liver paren- 
chyma into hepatic lobules which I have found has been in an 
embryo of 254-mm. in length. According to Engel (’99), this 
pig would be one at about full term, since he states that a pig 
at birth measures 25 em. Theopold (10), however, shows that 
pigs at full term vary considerably in length; that they even 
attain a length of 35 em. before birth. In the 254-mm. speci- 
men, the liver cells appear more vesicular, their protoplasm 
stains but faintly. The boundaries of the hepatic lobules as 
seen in figure 2 are in many places definitely marked. A close 
analysis of the dividing medium, however, shows that it con- 
tains no collagen fibrils, but rather its appearance is due to a 
change in the parenchyma. A higher-power drawing of this 
stage is shown in figure 3. To the right and left of the draw- 
ing are shown terminal hepatic on central veins; above and 
below are terminal portal veins. Extending from portal vein 
to portal vein is shown the first evidence of an interlobular 
septum. It consists of hepatic cells which are more coarsely 
granular and stain more deeply than the remaining cells; similar 
cells are found surrounding the portal veins. However, the 
thing which makes the septum most apparent is the arrange- 
ment of the cells. As seen in sections, they form two more 
or less regular parallel rows, an arrangement which becomes 
greatly accentuated in slightly older stages. Another factor 
which in places intensifies the distinctness of the septa is the 
presence of small branches of the portal veins. Nucleated 
blood-cells found in the sinusoids along the septa also aid in 
making it more distinct. I have studied carefully the retic- 
