THE PACE MAKER OF THE CARDIAC GANGLION OF LIMULUS POLYPHEMUS

Abstract

The ganglionated portion of the dorsal nerve cord on the heart of Limulus polyphemus, which is known to initiate the cardiac rhythm, is in every way comparable to the pace maker of the vertebrate heart. The actual initiation of impulses may, however, be restricted to a very small group of nerve cells, and it is shown that it is possible by experimental methods to shift this pace maker group to any level of the ganglionated cord. In each such case a coordinating mechanism forces the rest of the ganglion to assume the rate of impulse formation impressed upon it by the most active cells. Normally this pace maker group has no fixed location and is determined by fortuitous circumstances.