Franklin P. Mall - PEN 
lobules, representing the right and left lobes, with a vascular system in 
each identical in arrangement with that of a liver of one lobule. (Fig. 11.) 
When the umbilical vein first shifts from its entrance into the ductus 
Cuvieri to the hver it has taken the course in its new position, of the 
least resistance, as a glance at Fig. 15 shows. There is a mass, if not an 
excess, of capillaries in the liver at this time and this vein with its loose 
wall makes the change suddenly as is shown in Fig. 11. This brings 
to the liver an excess of blood which is followed by keeping open, or 
opening in case it has closed, the right omphalo-mesenteric vein. The 
continued growth of the liver and its capillaries increases the circulation 
Vv.o.m. 
jae, all Gaels 
Fic. 11. Semidiagrammatic reconstruction of the veins of the liver of a 
human embryo 4 mm. long (No. 186). JL, liver; wv, umbilical vein; vom, 
omphalo-mesenteric vein; i, intestine. 
Fic. 12. Semidiagrammatic reconstruction of the veins of the liver of a 
human embryo 6.5 mm. long (No. 116). L, liver; vom, right omphalo-mesen- 
teric vein; uv, umbilical vein; m, mesenteric vein; rhs, ramus hepatica sin- 
istra; ra, ramus angularis; i, intestine. 
in the distributing and collecting branches which is followed by their con- 
version into permanent venous trunks: first those on the left side and 
then those on the right side. The excess of blood is still continued and 
on account of the shifting of the right omphalo-mesenteric vein with the 
growth of the right lobe of the liver the route becomes circuitous, and a 
new and more direct channel, the ductus venous, is formed. This has 
