Fig. 8.4. A bundle of nerve fibers in layer 4 of the primary visual cortex of a 25 year old monkey. One of the nerve fibers is surrounded by a sheath of myelin that is only one lamella thick. The sheath is only three microns long. At each end of the sheath the nodes of Ranvier (nodes) are visible. The thickness of the sheath and the short length of the internode suggest that remyelination is occurring.
