A rhythmically discharging neuron in the earthworm ventral cord nerve as identified by lucifer yellow-CH injection.

In the process of mapping the ganglionic neurons in the earthworm ventral nerve cord by simultaneous recording and Lucifer Yellow-CH injection or by backfilling, a rhythmically discharging neuron with a continuous train of 100 cps over the entire recording period was encountered at the dorsal side of the cord near the base of the 2nd-3rd nerves, with its axon extending toward the 2nd-3rd contralateral nerves. It could not be determined whether branches of this axon entered these contralateral nerves. The rhythmic discharge could not be recorded extracellularly from the nerves or from the cord by suction or hook electrodes, nor did the cell respond to either intra- or extracellular stimulation through the recording and injection microelectrode. Although contralateral neurons have been described in histological works, this neuron may not be identifiable one of them until its relationship with other neurons becomes clear.