808 



DEVELOPMENT OF THE VASCULAR SYSTEM. 



or months. We have a specimen, taken from a child one year and nine 

 months old, in which the opening is still very distinct ; and it is not 

 unfrequent to find a small aperture existing even in adult life. In these 



Fig. 316. 



Diagram of the ADULT CIRCULATION THROUGH THE HEART. a, a. Superior and 

 inferior venae cavse. b. Right ventricle, c. Pulmonary artery, dividing into right and left 

 branches, d. Pulmonary vein. e. Left ventricle. /. Aorta. 



instances, although the adhesion and solidification of the inter-auricular 

 septum may not be complete, yet no admixture of blood takes place 

 between the right and left sides of the heart ; since the direction of the 

 passage is always very oblique, and its valvular arrangement prevents 

 any regurgitation from left to right. The complete filling of the left 

 auricle with arterial blood, returning from the lungs, also opposes a 

 complete obstacle to the entrance of venous blood from the right 

 auricle. 



