Compared with the mammal on the one hand, and with the lower types on the other, the venous circulation of the bird illustrates the following points: 1. Extensive reduction of the renal portal system and direct formation of postcava by the iliac veins, foreshadowing the condition found in the mammal. 2. Complete separation of the portal and systemic venous circulation in the adult. Disappearance of the ventral abdominal vein as a vessel of the body wall. =5. Human Foetus at Term.=--The student is recommended to examine, by dissection and injection, the venous system of a foetus at term, noting the following facts: 1. Course of umbilical vein in ventral abdominal wall and along free edge of falciform ligament to liver (Fig. 241), corresponding to the position of the amphibian and reptilian abdominal vein (Figs. 264 and 275). 2. Connection of umbilical vein in liver: (_a_) With portal system (Figs. 258 and 271). ({~GREEK SMALL LETTER ALPHA~}) With portal vein. ({~GREEK SMALL LETTER BETA~}) With portal system of left and quadrate lobes by branches derived directly from umbilical vein while situated in the umbilical fissure (Fig. 258). (_b_) With hepatic veins and postcava by the ductus venosus (Figs. 258 and 271). [Illustration: FIG. 271.--Human foetus at term. Corrosion preparation of heart and vascular system. (Columbia University Museum, No. 1858.)] 3. Connection of the postcaval and precaval systems by the azygos veins representing the proximal segments of the embryonic postcardinal veins (Fig. 272). [Illustration: FIG. 272.--Human foetus at term. Postcava and azygos veins. (Columbia University Museum, No. 1861.)] If possible the dissection of an injected foetus should be combined with the examination of corrosion preparation of the foetal circulation and especially of the venous system of the foetal liver (Figs. 258 and 271). 3. The remnants of foetal structures in the adult liver (round ligament and ligament of the ductus venosus) should be compared with the structures from which they are derived in the foetus at term (umbilical vein and ductus venosus). II. THE VENTRAL MESOGASTRIUM.