FIG. 331, A, B, AND C. DIAGRAM ILLUSTRATING THREE STAGES IN THE 

 DEVELOPMENT OF THE HEPATIC PORTAL SYSTEM. 



Az, azygos ; Ci, postcaval ; DA, ductus venosus ; DC, DC, precavals ; H, heart ; 

 Jl, iliac vein ; L, liver ; Me*, mesenteric vein, which later gives rise to the 

 hepaticportal (V.part), receiving blood from the alimentary canal (Mes, D) ; 

 JY, kidney ; Om, Om 1 , Om*, the three sections of the vitelline or omphalo- 

 mesenteric vein (the first still shows its originally paired nature at ft : in 

 stage B, the second section of this vein which passes through the liver, 

 disappears, so that Ow and Owz-are only connected by capillaries : in stage C, 

 the first section (Om) has quite disappeared, and the umbilical vein (Uml>) 

 has become developed ; Sv, sinus venosus ; Vad. advehent veins ; Vr, revehent 

 veins ; *, connection of the umbilical vein with the capillaries of the liver. 



