Since Nissl1 published his original article, the retrograde method has been widely employed in searching for the cells of origin of both central and peripheral neurons. On the basis of results obtained with this procedure, it is assumed that the power of withstanding axon injury is less in central than in peripheral neurons.2 The view that the so-called Betz cells of area 4 (motor cortex) give sole origin to the fibers of the pyramidal tract is based largely on the results of the retrograde approach, especially the study of Holmes and May.3 These investigators, as well as numerous others,4 unanimously reported the eventual breakdown and disappearance (atrophy) of the so-called giant cells of area 4 in several species of mammals following injury to the pyramidal fibers. As a corollary, neurons throughout the pyramidal tract should concomitantly vanish, with loss of giant cells. In disharmony with these
LASSEK AM. THE PYRAMIDAL TRACT: A STUDY OF RETROGRADE DEGENERATION IN THE MONKEY. Arch NeurPsych. 1942;48(4):561–567. doi:10.1001/archneurpsyc.1942.02290100061006
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