Wallerian degeneration: A reevaluation based on transected and colchicine‐poisoned nerves in the amphibian, Triturus

The sequence of degeneration in colchicine‐poisoned or in transected peripheral nerve fibers is reported. The results lead us to conclude that the Schwann cell is the predominant agent of axon and myelin destruction. The Schwann cytoplasm burgeons, swells the Schmidt‐Lanterman clefts and the adaxonal layer of cytoplasm, and invades the electron‐dense bands of myelin. The axolemma and adaxonal membranes are eroded and Schwann organelles invade the axoplasm commingling with those of the axon to form a peripheral “reactive zone.” The reactive zone of organelles surrounds a core of compacted neurofilaments which may persist for days. Eventually the entire contents, commingled organelles and neurofilaments, are destroyed. The myelin sheath is destroyed without being separated from its Schwann cell of origin.