Introduction

Abstract

Ever since their first detailed investigations on the structure of the central nervous system, the neuroanatomists, and particularly Ramón y Cajal, have been meditating on the mode of operation of the complex patterns of neuronal arrangements that they were discovering. These patterns appeared to be so different in the various regions of the nervous system, yet there seemed to be some underlying principles of organization which could dimly be perceived. Ramón y Cajal himself did not hesitate to draw conjectural diagrams of all the major neuronal assemblages that he investigated, and he proposed many modes of neuronal interaction. But inherent in all these diagrams of neuronal pathways was the fatal defect that inhibitory synaptic action was as yet not recognized. In his diagrams all synaptic actions were assumed to be excitatory. One can now contrast his operational diagrams of the cerebellar cortex (Ramón y Cajal, 1911, Figs. 103, 104; reproduced in Fig. 25) with those of Figs. 119, 120 and 121 below.