PHYSIOLOGY. 



39 



and the inner aspect of the chorion ; finally these 

 vessels enter into the vascular tufts found on the 

 external aspect of the chorion. From these vasculaf 

 tufts the numerous branches which meet to form the 

 umbilical vein take their origin. These unite to form 

 •one vein, which passes along the cord and enters the 



Fig. i8 



FcETAL Circulation: Advanced Period. 

 A, Placentulse; B', B', Umbilical Veins, with their Common Trunk, B; 

 D, Vena Porta, and its Anastomosis, C; E, Ductus Venosus, F, Pos- 

 terior Vena Cava; G, Right Ventricle of Heart; H, Pulmonary Artery; 

 J, J, Aorta; I, Ductus Arteriosus; K, Umbilical Arteries, with their 

 Anastomosis at the extremity of the Umbilical Cord . 



abdomen of the foetus at its umbilical opening. From 

 this situation it passes forwards, discharging its 

 contents into the fcetal heart. 



