Macrophage-mediated myelin stripping. A: Upon invasion of the Schwann cell tubes, macrophage processes (arrows) split the outer mesaxon in order to gain entry to the myelin spiral. B: They invade the myelin following the intraperiod line (arrow). Widening propagates centripetally towards the inner mesaxon. B: MS = myelin sheath; Scale bar = 2 μm.