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

 DEVELOPMENT OE THE HEPATIC PORTAL SYSTEM. 



Az, azygos ; Ci, postcaval ; J)A, ductus vt.-nnsus ; J)(\ 1)(\ precavals ; //, heart ; 

 .//, iliac vein ; L, liver ; jl/tx, mesenteric vein, which later gives rise to the 

 hepaticportal (V.jinrt), receiving blood from the alimentary canal (Mes, ]>) ; 

 A, kidney ; Out, Om l , Our, 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 Om and Our are only connected by capillaries : in stage C, 

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

 has become developed ; tir, sinus venosus ; Varl. advehent veins ; Vr, revehent 

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



