Abnormally high content of unmyelinated axon profiles in the ventral root L7 of a cat with an abdominal neoplasm.

The ventral roots of L7 of a cat with an intestinal neoplasm were examined electron-microscopically at different proximo-distal levels. The proportion of unmyelinated axon profiles was 50-55% at mid-root and distal levels as compared to 30% in normal adult cats. In the juxtamedullary root fascicles the proportion was normal (average 20%), and few unmyelinated axons seemed to penetrate into the CNS through the ventral root. The number of myelinated axons was within the normal range.