Elements of animal physiology, chiefly human . Fisf. 44. Diagram of the Circulation through theHeart (after Dalton.) VALVES OP THE HEART, 95 If the tops of the ventricles be cut off and the ven-tricles filled with water, the aorta and pulmonaryveins being tied, the thin membranous valves will bepressed upwards, becoming tightly stretched, and thewhole action of the valves clearly visible. 193. Valves of the Heart (from Lat. valvce, foldingdoors).—The valves are tough, flexible, membranousstructures, which are attached to the fibrous borders ofthe openings into the heart, and hetween its upper
Elements of animal physiology, chiefly human . Fisf. 44. Diagram of the Circulation through theHeart (after Dalton.) VALVES OP THE HEART, 95 If the tops of the ventricles be cut off and the ven-tricles filled with water, the aorta and pulmonaryveins being tied, the thin membranous valves will bepressed upwards, becoming tightly stretched, and thewhole action of the valves clearly visible. 193. Valves of the Heart (from Lat. valvce, foldingdoors).—The valves are tough, flexible, membranousstructures, which are attached to the fibrous borders ofthe openings into the heart, and hetween its upper andlower chambers. (See figs. 43 to 45.) They are so arranged as only to permit of the passage offluid in one direction, any attempt at reflux causing theblood to get behind the flaps or segments of the valves,and thus force them tightly against the openings, so asto close them the more efiectually in proportion as thebackward pressure is increased. But for the chordce Aortio Valve. Tdg\\i Coronary / Mitral Vah-e. Tricuspid Valve. Fig, 45, The Top of Heart, the Auricles being dissected off. iendince, the pointed flaps of the tricuspid and centralvalves would be driven through into the auricles. The valves which consist chiefly of connective tissue, 96 ANIMAL PHYSIOLOGY. are formed by tlie duplicature of the lining membraneof tlie interior of the heart, their substance beingstrengthened by an additional h\yer of fibrous tissue,possibly containing mnscnlar fibre. 194. The heart is supplied with six valves, ybwr of theprincipal of which, viz., the tricuspid and the pulmonarysemi-lunar valves of the right side of the heart, andthe mitral and aortic (semi-lunar) valves on the leftside, are shown in fig. 45. The right auricle also pos-sesses two other valves, viz., the coronary valve, whichguards the entrance of the coronary vein (see fig. 43),and the Eustachian valve, which protects the termina-tion of the inferior vena cava. 195. The tricuspid valve (from Lat. tres, thre
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