. Quain's elements of anatomy . set, formingtwo principal bundles, an anterior and a posterior, named musculijKipillares, are connected at their base with the ventricular wall, and bythe other end are attached to small tendinous cords {cliordce, iendinecR),through Avhich they are connected with the segments of the auriculo-ventricular valve. The inside of the conus arteriosus is smooth, and freefrom columnEc carnete. The valve guarding the right auriculo-ventricular opening is com-posed of three triangular segments, or flaps (right, left or infundibular,and posterior or septal), and is hence n
. Quain's elements of anatomy . set, formingtwo principal bundles, an anterior and a posterior, named musculijKipillares, are connected at their base with the ventricular wall, and bythe other end are attached to small tendinous cords {cliordce, iendinecR),through Avhich they are connected with the segments of the auriculo-ventricular valve. The inside of the conus arteriosus is smooth, and freefrom columnEc carnete. The valve guarding the right auriculo-ventricular opening is com-posed of three triangular segments, or flaps (right, left or infundibular,and posterior or septal), and is hence named the tricuspid. The flap-sare mainly formed of fibrous tissue covered by endocardium. Attheir bases, they are continuous with one another, so as to form anannular memlDrane attached around the margin of the auricular open-ing : they are directed downwards, and are retained in position withinthe ventricle by the chorda3 tendincEe, which are attached to theirventricular surfaces and free margins. The middle part of each seg-. 486 THE HEART. meiit is thicker than the rest, whilst the mrirginal part is thin, trans-parent, and jagged at the edges (compare fig. 428, B, e, e). The chordcG tendineaB from the anterior papillary muscle pass to the cleftbetween the right and left segments, to be attached to both: the chordas tendinecefrom the posterior papillary mnscle are attached in like manner to the right andposterior segments ; while others forming a third set spring directly from the sur-face of the septum, sometimes from small eminences upon it, and pass upwardsto be attached to the adjacent borders of the left and posterior segments. During the contraction of the ventricle, the segments of the valve are appliedto the opening leading from the auricle, and prevent the blood from rushingback into that cavity. Being retained by the chorda3 teudineee, the expandedflaps of the valve resist the pressure of the blood, which would otherwise forcethem back through the auricular orifice
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