THE HUMAN PYRAMIDAL TRACT

The many investigators of the human pyramidal system have been handicapped in not being able either to produce experimentally or to obtain from autopsy material a pure lesion of the corticospinal tract. Until such an isolated lesion can be studied, it is difficult to evaluate what the exact role of this bundle may be in man. Many of the lesions affecting the corticospinal tract occur high up in the central nervous system, in the region of complex, and as yet largely unknown, structures. It seemed possible that, irrespective of the etiologic and pathologic factors, the pyramidal axons might not be completely destroyed in all cases of unilateral paralysis, whether the latter is called hemiplegia or hemiparesis or sometahing else. How many axons, if any, must be missing in the pyramid to produce muscular dysfunction or the abnormal Babinski sign I have not found stated in the literature. With these considerations