DISSECTION OF THE BACK AND THORAX. 



125 



and the clots of blood having been cleared out, the cavity will be 



ready for examination. 



The Cavity of the Right Aueicle. The interior of this and the 



other cavities of the heart is smooth and glistening in virtue of an 



endothelial membrane termed the endocardmm, which is here continuous 



with the endothelial lining of the great veins. It will be observed that 



the muscular wall of the auricle is thrown into parallel ridges, which 



from their resemblance to the 



teeth of a comb are termed 



rmtsculi pectinati. The venous 



orifices by which the blood is 



poured into the cavity are all 



found in the sinus venosus, 



and are as follows : — 1. The 

 anterior vena cava empties 

 itself into the anterior part of 

 the roof of the sinus. 2. The 

 posterior vena cava discharges 

 itself at the lower- and back 

 part of the outer wall of the 

 sinus. 3. The coronary ven- 

 ous sinus conveys the blood 

 from the wall of the heart it- 

 self, and its mouth will be 

 found under that of the pos- 

 terior vena cava. 4. The vena 

 azygos sometimes has an in- 

 dependent opening into the 

 auricle, and it then discharges 

 itself by the roof of the sinus, 

 behind the mouth of the 

 anterior cava. At other times 



it opens into the anterior Auricular appen'dix. 



cava. 5. The ven<e cordis , . , . , ^ 



mininue are small veins of the wall of the right auricle, which, instead 

 of discharging themselves by the coronary sinus, open directly on 

 the wall by minute mouths named the foramina Thebesii. Of ail 

 these orifices, that of the coronary sinus is the only one provided with 

 a valve. It is a thin fold of the lining membrane, termed the valve of 



The inner wall of the sinus venosus is formed by the auricular sep- 

 tum, which is the partition between the two auricles. On this the 

 following objects are to be noticed:-!. Between the orifices of the 

 anterior and posterior cav* is a muscular prommence-the tuhercle of 



Fig. 9. 



diageam of the two cavities of the eioht side 

 OF THE Heart (Ellis), 

 a Anterior cara ; b. Posterior cava ; c. Eight auriculo- 

 ventricular opening ; d. Fossa ovalis ; e. Opening of 

 the coronary sinus ; /. Foramina Thebesii, the openings 

 of veins ; a. Aperture of the pulmonary artery ; h. 



