. The structure and life of birds . TV -. Fig. 21.—(it) Birds heart showing valve between right auricle and right ventricle.(b)—modified from Quain—Mans heart showing the same, lv, wall of left ventricle ;RV, right ventricle ; TV, tricuspid valve ; v, valve. In the human heart it is called the mitral valve fromits fancied resemblance to a bishops mitre. Thereare other valves as well without which the heart wouldbe very imperfect. There must be some means of pre-venting the blood when it is driven into the two greatarteries, the aorta and the pulmonary, from returningto the heart. The entrance
. The structure and life of birds . TV -. Fig. 21.—(it) Birds heart showing valve between right auricle and right ventricle.(b)—modified from Quain—Mans heart showing the same, lv, wall of left ventricle ;RV, right ventricle ; TV, tricuspid valve ; v, valve. In the human heart it is called the mitral valve fromits fancied resemblance to a bishops mitre. Thereare other valves as well without which the heart wouldbe very imperfect. There must be some means of pre-venting the blood when it is driven into the two greatarteries, the aorta and the pulmonary, from returningto the heart. The entrance to each, therefore, isguarded by three semilunar valves, little pocketswhich look outwards, away from the heart, and, con- 74 THE STRUCTURE AND LIFE OF BIRDS chap. sequently, close against an inrush of blood, but allowan outrush to pass. In a bird of any size they areeasy to see. Some account of a reptiles heart will be found inthe chapter on The Bird within the Egg. The Blood. Cut off the supply of blood from a limb, and all itspo
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