Selection of pathways by regenerating spinal cord fiber tracts.

We have traced fiber tracts in the regenerating teleost spinal cord and have found that the regenerative capabilities of fiber tracts coming from different parts of the CNS vary considerably. Some descending tracts can regenerate up to 5.6 mm beyond a transection, while other fiber tracts cannot even penetrate the scar tissue. In spite of a great disturbance of their normally ordered pathways as they grow through the lesion site, those tracts which can regenerate can find their appropriate funiculi in the distal spinal cord.