FROM current electrophysiological studies, it has been concluded that the major, if not the exclusive, source of climbing fibers of cerebellar cortex lies in the inferior olive,1-3 a view also espoused upon anatomical grounds by Szentágothai and Rajkovits.4 The early literature related to this topic was largely anatomical and contained conflicting evidence concerning which of the extrinsic systems leading to cerebellum could be presumed to end as mossy and which as climbing fibers. For example, Ramón y Cajal believed that the pontocerebellar system ends as climbing fibers, while Lorente de Nó6 proposed that all incoming paths end as mossy fibers, reserving for the climbing ones the termini of the short inter cortical systems.
Much of the evidence acquired since has used a reduced silver method to display terminal degeneration consequent upon interruption of one of the entering systems at its source. In general, the reduced silver