THE HUMAN PYRAMIDAL TRACT

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Abstract
With few exceptions, elementary and clinical textbooks of human neurology describe the pyramidal tract fibers as arising solely from the Betz, or gigantopyramidalis, cells of the motor area (area 4). Some investigative work, however, suggests that this may not be the case. Campbell,1 counting only every fifth section which came from the microtome, roughly estimated the number of Betz cells in the motor area of man as 25,000. Using the Bielschowsky technic, Weil and Lassek2 calculated the number of corticospinal fibers entering the spinal cord as 250,000, or approximately ten times the number of cells reported. Recently, Lassek and Rasmussen,3 employing the silver technic of Davenport and his co-workers,4 reported that slightly over 1,000,000 of these axons descended into the cord on one side in each of 3 brains. In view of this marked discrepancy, an attempt has been made to determine, as exactly as possible,