264 A Study of the Structural Unit of the Liver 
and third order date from the beginning of the dovetailing process. A 
word more about the vena cava inferior. In its beginning it belongs en- 
tirely to the liver and is completely surrounded with liver tissues. In the 
adult liver two small branches empty into it in addition to the main 
branches mentioned above. The first is closely associated with the vena 
hepatica media accessoria. The other arises from the omental lobe and 
Fic. 25. Ventral view of a reconstruction of the vasicular system of the 
embryo 11 mm. long (No. 109). X 25. Uv, umbilical vein; pv, portal vein; 
rad, ramus angularis; ru, recessus umbilicalis; rd, ramus descendus; ra, ramus 
arcuatus (possibly ramus ascendus); rc, right arborization of the recessus 
umbilicalis; r/7, left arborization of the recessus umbilicalis; dv, ductus veno- 
sus; vc, vena cava; vom, omphalo-mesenteric vein; 7m, ramus media; rs, 
ramus sinistra. 
usually goes directly to the vena cava, but occasionally communicates 
with the vena hepatica sinistra. It is seen that the vena cava collects 
blood directly from the quadrate and Spigelian lobes. 
