316 



DISSECTION OF THE THORAX. 



and its extremities are the openings of the superior and inferior cava*. 

 Between those vessels the cavity projects a little, and presents a slight 

 elevation in some bodies (tubercle of Lower). The apex is prolonged 

 downwards towards the junction of the auricle with the ventricle, andm 

 it is the opening into the right ventricular cavity. 



The anterior wall is thin and loose. Near its upper part is an opening 

 leading into the pouch of the appendix or auricula (//), which will admit 

 the tip of the little finger. Around and in the interior of the appendix, 

 are fleshy bands, named musculi pectinati, which run mostly in a trans- 

 verse direction, and form a network that contrasts with the general smooth- 

 ness of the auricle. 



Fig. 100. 



a. Upper cava. 



b. Lower cava. 



c. Right auriculo-veutricular opening. 



d. Fossa ovalis. 



e. Opening of the coronary sinus. 



/. Foramina Thebesii, the openings of veins. 

 g. Aperture of the pulmonary artery. 

 h. Auricular appendix. 



DIAGRAM OF THE TWO CAVITIES op THE RIGHT SIDE OF THE HEART. 



The posterior wall corresponds for the most part with the septum be- 

 tween the auricles, in consequence of the position of the heart. On it, 

 close to the inferior cava, is a large oval depression, the fossa ovalis (?), 

 which is the remains of an opening between the auricles in the foetus. In- 

 feriorly it merges into the lower cava. A thin semi-transparent structure 

 forms the bottom of the fossa; and there is oftentimes a small oblique 

 aperture at its upper part. Around the upper three-fourths of that hollow 

 is an elevated band of muscular fibre, called annulus sen isthmus Vieus- 

 senii, which is most prominent above and on the left side, and gradually 

 subsides inferiorly. 



Altogether at the lower part of the posterior wall is the aperture of the 

 coronary sinus (e). Other small apertures are scattered over this surface : 

 some lead only into depressions ; but others are the mouths of veins of the 

 substance of the heart (venae cordis minima}), ami are named foramina 

 Thebesii (/). 



Tin- chief apertures in the auricle are those of the two cavre, coronary 

 sinus, and ventricle. The opening of the superior cava (a), is in the front 



