Abstract
The neurotoxic effects of tricresylphosphate on the ventromedial tract of the spinal cord in hens was examined with light and electron microscopy. Degenerative changes at the ultrastructural level of these myelinated fibers were correlated with the results obtained by light microscopy. The fine-structural changes were first noted in the form of swelling and loss of internal cristae of mitochondria, followed by shrinkage and disappearance of neurofilaments in the axoplasm, and finally the disintegration of myelin sheath itself. We suggest that a full axonal flow is more important for the maintenance of normal myelin sheath than the local integrity of the neuroglia cells.