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The pulsation of the eel’s heart can easily be seen externally on the ventral surface of the body a short way behind the pectoral fins. There are no rigid structures of any kind between the integument and the heart. W hen the very tough and resistant skin is cut through and the great lateral muscles are separated from each other, the pericardium is seen, loosely adherent to the surrounding tissues. The pericardial cavity being laid open, the various parts of the heart, abundantly lubricated with fluid, come into view.

II. On the structure and rhythm of the heart in fishes, with especial reference to the heart of the eel