The giant axon of the squid provides a unique cell biological model for analyzing the
biochemistry and cell biology of the axon. These axons may exceed 500 μm in diameter and
can be readily dissected. Once the surrounding small axons and connective tissue are
removed, the axoplasm can be extruded as an intact cylinder of isolated cytoplasm. This
isolated axoplasm is morphologically indistinguishable from the intact axon, but without
permeability barriers. Fast axonal transport will continue for more than 4 h after extrusion …