Giant Neurons and Axon Pathways in the Brain of Tritonia

Abstract

1. The anatomy and histology of the brain of Tritonia hombergii are described. 2. The brain contains giant neurons which are regularly found in the same positions: cerebral ganglia, one in each; pleural, nine; pedal, eight; buccal, two. 3. The two cerebral giant neurons show spontaneous activity which is inhibited by stimulation of the cerebral nerves. The two largest cells in the pleural ganglia are not spontaneously active but have orthodromic excitatory connexions with axons in the pleural nerves. 4. The branching of the axons of the giant cells has been followed using electrophysiological methods. The axons of a particular giant cell are distributed in a symmetrical fashion to nerves arising on both sides of the brain. This pattern of distribution is similar to that of the corresponding cell in the opposite half of the brain.