The admirable study of Holmes and May ( '09) established the origin of the pyramidal tract from the large cells of the motor area (area 4 of Brodmann) which were originally described by Retz (1874). These authors found in a series of mammals that, after hemisection of the spinal cord, retrograde cell degeneration occurred only in large infragranular cells of this area of the cerebral cortex. Examination of human pathological material by them and by Wohlfahrt ('32) confirmed this localization of the origin of the pyramidal tract in man.
That the precentral gigantopyramidal area gives rise to the bulk of the cortico-spinal fibers has generally been accepted. But the view continually appears that there might be other sources of these fibers. Schroder ('14), Kennard ('35) and Hoff ('35) with different methods found evidence for the origin of some cortico-spinal fibers in the premotor area. Vogt ('06) examined with the Marchi method the brain of a monkey with a postcentral lesion and found degeneration of a small bundle of fibers in the posterior limb of the internal capsule. H.e designated these fibers as pyramidal, but did not IAided by a grant from the Committee on Scientific Research of the American Medical Amsociation. 411 THE JOVUNAD Or COMPARATIVE NLUROLOCY, VOL. 68, NO. 4
' A s one of the authors has expressed previounly (Lerin, '36), the only corticifugal tract that may properly be termed 'pyramidal' is that which passes through the bulbar pyramid, the cortico-spinal tract. Other corticifugal tracts which end in tho brain stem are best called 'extrapyramidal.'