Abstract: Anterograde degeneration of the pyramidal tract has been studied with the cupric silver method, the Fink-Heimer method procedure Ⅱ and bleaching of Fink-Hcimer method in 15 rabbits after lesions of frontal and parietal cortex. Degenerated fibers and terminals were observed under microscope and recorded by camera lucida. Experimental results showed that heavy degenerated fibers were found in the ipsilateral pyramid. Degenerated fibers crossed to the opposite side in the pyramidal decussation and lay within the gray matter of the dorsal horn in segments C₁～C₅. In segment C₁ heavy degenerated fibers mainly distributed in laminae Ⅲ～V of the spinal cord. Degenerated fibers gradually decreased and limited in lateral part of laminae V in segments C₂～C₅. Degenerated terminals were distinguished definitely in laminae Ⅲ～V throughout segments C₁ and C₂. The resultssuggested that location of the pyramidal tract may reflect an aspect of evolution in mammals.

Key words: cerebral cortex, pyramidal tract, spinal cord, anterograde degeneration, rabbit