The Path of the Giant Cell Axons in Aplysia depilans

Abstract

THE presence of large nerve cells in the abdominal ganglion of Aplysia has provided a valuable preparation for the study of the physiology of invertebrate neurones^1–8. The largest cell is usually referred to as the giant nerve cell^1–3,6–8 and it may be 300–800µ in diameter. It is excited synaptically by pathways entering most, if not all, of the nerves of this ganglion, but its only efferent axon passes anteriorly along the right pleuro-visceral connective. As almost all the work on the abdominal ganglion has been done with it completely isolated from the rest of the nervous system, the further path of this axon and the possible functions of this very large cell have not been understood. Experiments, which included the insertion of micro-electrodes into this giant cell when the abdominal ganglion retained its functional connexions with the rest of the nervous system in a whole animal preparation, have provided evidence for the branching of this axon and have excluded certain possibilities concerning the function of the giant cell.