472 



THE BLOOD-VASCULAR SYSTEM. 



this vessel it descends to supply the lower extremities and viscera of the abdo- 

 men and pelvis, the chief portion being, however, conveyed by the umbilical 

 arteries to the placenta. 



From the preceding account of the circulation of the blood in the foetus it will 

 be seen 



1. That the placenta serves the purposes of nutrition and excretion, receiving 



Ductus arteriosus. 



Internal iliac artery. 



FIG. 279. Plan of the foetal circulation. In this plan the figured arrows represent the kind of blood, as 



well as the direction which it takes in the vessels. Thus, arterial blood is figured ~^ > ; venous blood, 



"^ > ; mixed (arterial and venous) blood, }> >. 



the impure blood from the foetus, and returning it charged with additional nutri- 

 tive material. 



2. That nearly the whole of the blood of the umbilical vein traverses the liver 



