THE HEART AND MEDIAN CARDIAC NERVE OF LIMULUS POLYPHEMUS

Abstract

Using the cathode ray oscillograph in association with an amplifier as a recording mechanism, the heart and median cardiac nerve were studied in vivo and in vitro. The ventricle freed of ganglion cells contracts rhythmically if normally distended. The contraction of the normally innervated ventricle is practically simultaneous throughout its length. The contraction wave of the deganglionated ventricle propagates as a slow peristalsis. The adult heart is neurogenic; it consists essentially of an atrium and a ventricle, each of which is contractile. The po tential of the median cardiac nerve consists essentially of 2 components, one derived from the axons of large pacemaker ganglion cells, the other from the axons of small motor ganglion cells. The spontaneous activity of the ganglion cells of the median nerve cord is oscillatory in type. An analysis of the ventricular electromyogram shows the contraction process to be a tetanus. Records have been made of the effect of the extrinsic nerves on the potential of the median cardiac nerve. A scheme of the manner of action of the intrinsic ganglion cells of the median nerve cord upon each other and of the extrinsic nerves on the intrinsic nerve mechanism is presented. The findings of this research are discussed from the standpoint of comparative heart physiology.