RIGHT VENTRICLE. 473 



The Musculi pectinati are small muscular columns situated in the 

 appendix auriculae. They are very numerous, and are arranged 

 parallel with each other; hence their cognomen, " pectinati" like 

 the teeth of a comb. 



The RIGHT VENTRICLE is 'triangular and three-sided in its form. 

 Its anterior side is convex, and forms the larger proportion of the 

 front of the heart. The inferior side is flat, and rests upon the dia- 

 phragm : and 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 par- 

 allel with, and a little to the right of, the middle line, from the pul- 

 monary 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 tricuspid valves. They may be thus arranged : 



Auriculo-ventricular opening, 

 Opening of the pulmonary artery. 

 Tricuspid valves, 

 Semilunar valves. 

 Chordae tendineas, 

 Carneae 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 sep- 

 tum 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- 

 brane, 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 at- 

 tachment to a number of slender tendinous cords, called chordae 

 tendinese. The chordae tendinece are the tendons of the thick mus- 

 cular columns (columnce carnecR) 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 attachment. 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 chordse tendinae 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 mere folds of lining 

 membrane, viz. the semilunar, Eustachian, and coronary. 



Mr. T. W. King, of Guy's Hospital, has made tlie tricuspid 



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