DEVELOPMENT OF THE CIRCULATORY SYSTEM. 



937 



intense to give rise to an inspiratory effort, and the first inspiration is made. The pul- 

 monary organs are then, for the first time, distended with air, the pulmonary arteries 



Pulmonary Art, 



Foramen Ovale. / 



Eustachian Valve.- (- 

 Right Auric. -Vent. Opening. 





y Art. 



Left Auricle. 

 Left Auric. - Vent. 



Hepatic Vcin.^ 



Branches of the /"'--.. Liver. 



Umbilical 



to the Liver. 



Bladder. 



\/ 



Internal Iliac Arteries. 

 FIG. 311. Diagram of the fo&tal circulation. 



carry the greatest part of the blood from the right ventricle to the lungs, and a new cir- 

 culation is established. During the later periods of fetal life, the heart is gradually pre- 

 pared for the new currents of blood. The foramen ovale, which is largest at the sixth 



