The Early Changes in the Axoplasm during Wallerian Degeneration

Axoplasmic changes were studied in the saphenous nerve of the albino rat during the early stages of Wallerian degeneration. The axons were examined at 0, 24, and 48 hours after the surgical transection of the nerve. The material was fixed in 2 per cent OsO(4) in phosphate buffer (pH 7.2–7.5) with sucrose (added to a final osmolar concentration of ∼0.37 M). The earliest changes were seen in the endoplasmic reticulum which became fragmented into rows of small vesicles. Then, between 24 and 48 hours, the neurofilaments underwent complete disintegration and the axoplasm became filled with finely granular material which later formed irregular clumps surrounded by a structureless matrix, probably fluid in vivo. The fragmentation of the neurofilaments was accompanied by pronounced swelling of the mitochondria.