The physiology of the circulation in plants : in the lower animals, and in man : being a course of lectures delivered at surgeons' hall to the president, fellows, etc of the Royal college of surgeons of Edinburgh, in the summer of 1872 . by the blood forcedby the auricles into the ventricles ; the neutral state, to that almostinappreciable interval which succeeds the sudden closure of theventricles, in which the blood set in motion is arranged in spiralcolumns, and acts in such a way as not only instantly closes thevalves, but screws and tvedges the segments thereof into each 230 Dll J. BELL T
The physiology of the circulation in plants : in the lower animals, and in man : being a course of lectures delivered at surgeons' hall to the president, fellows, etc of the Royal college of surgeons of Edinburgh, in the summer of 1872 . by the blood forcedby the auricles into the ventricles ; the neutral state, to that almostinappreciable interval which succeeds the sudden closure of theventricles, in which the blood set in motion is arranged in spiralcolumns, and acts in such a way as not only instantly closes thevalves, but screws and tvedges the segments thereof into each 230 Dll J. BELL TETTIGREW ON THE other? in an upward spiral direction. The active state correspondsto the period occupied by the progressive closing of the this period, the valves are dragged forcibly downwards by theshortening of the musculi papillares, in an opposite direction to thatby which they ascended; and are tvnsted into or round each other, toform spiral dependent cones. In the active stage, as in the neutral,the blood acts from beneath, and keeps the delicate margins andapices of the segments of the valves in accurate contact. Theappearances presented are represented at Figs. 141,142,143, and 144. Pig. 141. Fig. Figs. 141,142, and 143, show the mitral (r s) and tricuspid (min) valves in action (human):how the segments, acted upon by the spiral columns of blood, roll up from beneath towardsthe end of the diastole (Fig 141) • how, at the beginning of the systole, they are wedged andtwisted into each other, on a level with the auriculo-ventricular orifices (Fig. 142); andhow, if the pressure exerted be great, they project into the auricular cavities (Fig. 143).When the mitral and tricuspid valves (Fig. 141, mm, op) are open, the aortic and pulmonicsemilunar valves (v w x, r s i)are closed. When, on the other hand, the mitral and tricuspidvalves are closed (Figs. 142, 143, and 144, r s, mi n), the aortic and pulmonic semilunar ones(v w x,r s t) are open. To this
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