THORAX 



Right auricle (O.T. appendix) 

 Orifice of superior 



vena cava 



the intervenous tubercle (Lower), which tends to throw the 

 stream of blood entering the atrium by the superior vena 

 cava downwards and forwards into the atrio- ventricular 

 orifice. 



The orifice of the inferior vena cava is in the lower and 

 posterior part of the atrium, at the level of the sixth right costal 



cartilage * and the 

 lower border of the 



Superior vena cava -111 



eighth thoracic 

 vertebra. Running 

 along its anterior 

 margin, and inter- 

 vening between it 

 and the atrio-ven- 

 tricular opening, is 

 the remnant of a 

 valve, the valve of 

 the vena cava 

 (Eustachii). (Figs. 

 42, 44.) It ter- 

 minates, to the left, 

 in the lower end of 

 a ridge, limbus fossa, 

 ovalis (O.T. annulus 

 ovalis}, which 

 lies on the inter- 

 atrial septum and 

 forms the anterior 

 and upper bound- 

 ary of a shallow 

 FIG. 44. Interior of Right Atrium as seen by the fossa, the fossa 



removal of the anterior wall, or that wall op- ovalis 



posed to the base of the Ventricles. This is \ 



a part of the same specimen that is depicted 



Crista terminalis 



Intervenous 

 tubercle 



Limbus ovalis 



Fossa ovalis 



Left atrio- 

 ventricular orifice 



Opening of 

 coronary sinus 



Coronary valve 



Valve of inferior 

 vena cava 

 (Eustachii) 



Cut edge of 

 at rial wall 

 Inferior vena cava 



(Figs. 42, 

 44). At the upper 



in Fig. 43. end of the fossa 



ovalis there was, 



during fcetal life, a foramen, the foramen ovale, through which 

 the two atria communicated with each other. The object of 

 the valve of the vena cava, which in fcetal life was much 

 more perfect, was to direct the oxygenated inferior caval 

 blood through the foramen ovale into the left atrium, whence 



1 In the specimen shown in Fig. 46 it was at the level of the seventh 

 costal cartilage. 



