EM of the retro-orbital distal segment of rat optic nerve of the saline injected control animal immediately after the injection. Axoplasm of the myelinated axons contain numerous neurofilaments, microtubules, mitochondria and various other organelles. The transverse sections (A, Bar = 5 μm and B, Bar = 2 μm) show compact arrangement of the myelin lamellae around the axons in the internodal regions. The longitudinal sections show parallel running myelinated axons (C, Bar = 5 μm). Axon-myelin relationship in the nodal-paranodal region is better appreciated at very high magnification (D, Bar = 1 μm) Here, myelin terminal loops are seen attached to the paranodal axolemma on either side of the node.