534 RIGHT VENTRICLE. 



The Fossa ovalis is an oval depression corresponding with the 

 foramen ovale in the foetus. This opening is closed at birth by a thin 

 valvular layer, which is continuous with the left margin of the an- 

 nulus and is frequently imperfect at its upper part. The depression 

 or fossa in the right auricle results from this arrangement. There is 

 no fossa ovalis in the left auricle. 



The Tuberculum Loweri* is the portion of auricle intervening be- 

 tween the openings of the superior and inferior cava. Being thicker 

 than the walls of the veins it forms a projection, which was supposed 

 by Lower to direct the blood from the superior cava into the auriculo- 

 ventricular opening. 



The Musculi pectinati are small muscular columns situated in the 

 appendix auriculae. They are numerous, and are arranged parallel 

 with each other ; hence their cognomen, " pectinati" like the teeth of 

 a comb. 



The RIGHT VENTRICLE is triangular and prismoid in form. Its an- 

 terior side is convex, and forms the larger proportion of the front of the 

 heart. The posterior side, which is also inferior, is flat, and rests 

 upon the diaphragm ; the inner side corresponds with the partition 

 between the two ventricles, septum ventriculorum. 



The right ventricle is to be laid open by making an incision parallel 

 with, and a little to the right of, the middle line, from the pulmonary 

 artery in front, to the apex of the heart, and thence by the side of the 

 middle line behind to the auriculo- ventricular opening. 



It contains, to be examined, two openings, the auriculo-ventricular 

 and that of the pulmonary artery ; two apparatus of valves, the tri- 

 cuspid and semilunar ; and a muscular and tendinous apparatus be- 

 longing to the tricuspid valves. They may be thus arranged : 



Auriculo-ventricular opening, 

 Opening of the pulmonary artery. 



Tricuspid valves, 

 Semilunar valves. 



Chordaa tendinese, 

 Carnese columnae. 



The Auriculo-ventricular opening is surrounded by a fibrous ring, 

 covered by the lining membrane of the heart. It is the opening of 

 communication between the right auricle and ventricle. 



The Opening of the pulmonary artery is situated close to the septum 

 ventriculorum, on the left side of the right ventricle, and upon the 

 anterior aspect of the heart. 



The Tricuspid valves are three triangular folds of the lining mem- 



* Richard Lower, M-D- " Tractatus de Corde; item de Motu et Colore 

 Sanguinis," 1669. His dissections were made upon quadrupeds, and his ob- 

 servations relate rather to animals than to man. 



