Very few, if any, fibers of the crossed pyramidal tract extend throughout the entire length of the spinal cord in the cat. The tract terminates largely in the upper 2/3 of the spinal cord. There is evidence that many of its fibers terminate high in the cervical region of the cord. Many fibers are normally present in the pyramidal area of the cord which do not belong to any part of the pyramidal system including the so-called homolateral corticospinal component. Degeneration of axons of the pyramidal tract in the cat was detected as early as three days by the protargol method of staining. Cellular activity of the supporting elements continues for nine months or more in the pyramids following massive, cortical ablation. In its phylogenetic development the pyramidal tract in the cat appears to occupy a position intermediate between the lower mammals and man.