FCETAL CIRCULATION. 



709 



ventricle reaches the aorta by the ductus arteriosus, and only a 

 very small part goes to the lungs, to be returned from them by 

 the pulmonary veins to the left auricle. 



FIG. 291. 



Diagram illustrating the circulation through the heart and the principal 

 vessels of a foetus. (Cleland.) a. Umbilical vein. 6. Ductus venosus. /. 

 Portal vein. e. Vessels to the viscera, d. Hypogastric arteries, c. Ductus 

 arteriosus. 



The blood from the ductus arteriosus blends, therefore, with 

 that in the aorta which is passing to the viscera and lower ex- 

 tremities. The main part of this blood travels by two large 



