RIGHT VENTRICLE. 479 



tion, which was supposed by Lower to direct the blood from the superior 

 cava into the an riculo- ventricular opening. 



The Musculi pectinati are small muscular columns situated in the ap 

 pendix auriculoe. 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 anterior 

 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 dia- 

 phragm ; 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 tricuspid and 

 semilunar ; and a muscular and tendinous apparatus belonging to the tri- 

 cuspid valves. They may be thus arranged : 



Auriculo-ventricular opening, 

 Opening of the pulmonary artery. 



Tricuspid valves, 

 Semilunar valves. 



Chordae tendinese, 

 Carnese columnae. 



The Jluriculo-ventricular opening is surrounded by a fibrous ring, co- 

 vered by the lining membrane of the heart. It is the opening of commu- 

 nication 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 membrane, 

 strengthened by a thin layer of fibrous tissue. They are connected by 

 their base around the auriculo-ventricular opening ; and by their sides and 

 apices, which are thickened, they give attachment to a number of slender 

 tendinous cords, called chordae tendinese. The chorda tendinece are the 

 tendons of the thick muscular columns (columnce carnece) which stand out 

 from the walls of the ventricle, and serve as muscles to the valves. A 

 number of these tendinous cords converge to a single muscular attach- 

 ment. The tricuspid valves prevent the regurgitation of blood into the 

 auricle during the contraction of the ventricle, and they are prevented 

 from being themselves driven back by the chordae tendinese and their 

 muscular attachments. 



This connexion of the muscular columns of the heart to the valves has 

 caused their division into active and passive. The active valves are the 

 tricuspid and mitral ; the passive, the semilunar and coronary. 



The valves consist, according to Mr. King,* of curtains, cords, and 



* "Essay on the Safety Valve Function in the Right Ventricle of the Human Heart," 

 by T. W. King. Guy's Hospital Reports, vol. ii. 



