Before revision:  Clearance involves three structures that extend down the length of the nerve: glia, extracellular space, and axon and so need to be described in the tradition of the ' cable equations' of nerve used to explain nerve conduction since the work of Hodgkin in 1937.
After revision:  Clearance involves three structures that extend down the length of the nerve: glia, extracellular space, and axon and so need to be described as systems distributed in space in the tradition used for electrical potential in the ` cable equations' of nerve used to explain nerve conduction since the work of Hodgkin in 1937.