Physiology and biochemistry in modern medicine . , the first thing we mustdo is to establish the structural relationship between cold-blooded andwarm-blooded hearts. In the embryo of both classes of animals the 132 Tin; iiivsioi,o(JY (if tiik iikakthkat 183 heart arises as the so-called cardiac tube. As developmenl proceeds,diverticula grow ou1 Erom the walls of this tube to form the auricles and ventricles. In the comparatively simple heart of the turtle these dispo-sitions of the auricles and ventricles in relationship to the cardiac tubeare more or less evident even in the fully developed h
Physiology and biochemistry in modern medicine . , the first thing we mustdo is to establish the structural relationship between cold-blooded andwarm-blooded hearts. In the embryo of both classes of animals the 132 Tin; iiivsioi,o(JY (if tiik iikakthkat 183 heart arises as the so-called cardiac tube. As developmenl proceeds,diverticula grow ou1 Erom the walls of this tube to form the auricles and ventricles. In the comparatively simple heart of the turtle these dispo-sitions of the auricles and ventricles in relationship to the cardiac tubeare more or less evident even in the fully developed heart, particularlyin the case of the auricles (Fig. 49); but in the heart of the highermammalia it is impossible by superficial examination alone to show anyremains of the primitive cardiac tube. More careful anatomic investiga-tions during recent years have, however, shown that it exists in the formof certain definite structures composed of tissue histologically quite dif-ferent from that of the rest of the heart, and disposed in such a manner. Fig. 49.—Heart of tortoise as suspended. B, body of tortoise; TH, threads to levers; CL, clampholding aorta; A, auricle; C, coronary nerve; S, sinus; V, ventricle. (From Gaskell.) as would indicate not only that it is derived from the primitive cardiactube, but also that it is the main pathway along which the beat istransmitted. This primitive cardiac tissue is much better developed in certain re-gions than in others, the first portion of it to be discovered being thatknown as the auric uloventricular node, or the node of Stanley Kent* ( and 51). This structure is found at the base of the interauricular sep-tum on the right side and near its posterior margin. It exists as a collectionof peculiar small primitive cells and fibers, and is continued downward asa bundle of the same peculiar tissue to the interventricular septum,where, near the union of the posterior and median flaps of the aortic The discovery of this node is often
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Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectphysiology
