Function of Giant Mauthner's Neurons in the Lungfish.

Unit spikes were recorded from the spinal cord of the lungfish Protopterus and were identified with Mauthner's axon. With these spikes occurred nongraded tail flips suggesting startle responses. The tail flip and the giant spike resulted from certain forms of jarring and prodding. The conduction velocity for the slightly myelinated. 45 micro diameter fibers was 18.5 m/sec.