512 



THE BLOOD-VASCULAR SYSTEM 



of endocardium on the septal wall of the left atrium; it is called the valvula 

 foraminis ovalis. 



Posteriorly into the right atrium [atrium dextrum (fig. 425)], above and below, 

 respectively, open the superior and the inferior vena cava. Upon the septal 

 wall, immediately above the inferior cava is the fossa ovalis, a depression of 



Fig. 426. — Section of the Ventricles in Systole and Diastole. (After Krehl.) 



^ 



which the floor is formed by the meml)ranous septum. Surrounding the fossa 

 ovalis except below (indeed producing the fossa) is the limbus fossa) ovalis 

 which is continuous anteriorly and below with the valvula venae cavae (inferioris 

 Eustachii). Just anterior to the fossa ovalis is the orifice of the coronary sinus 

 guarded by the valvula sinus coronarii (Thebesii) (fig. 428). Leading from the 



