For a century, the neuron doctrine has been the basis for our concepts of nervous organization and brain function, stating that the cell theory applies to the nervous system. Santiago Ramon y Cajal, Spain's greatest scientist, was its main architect; his main tool being a capricious nerve cell stain discovered by Camillo Golgi. This book reviews the original papers on which the neuron doctrine was based, showing that the evidence came from such contributors as Albrecht Kolliker, Sigmund Freud, Wilhelm His, August Forel, Fritdjof Nansen and Gustav Retzius. Many questions were raised which remain relevant today. Electron microscopical studies in the 1950s appeared to confirm the classical doctrine but subsequent studies revealed unsuspected complexities. This book reviews the new studies against the classical work and suggests new directions for revising our concept of the neuron as a basis for the functional organization of the nervous system.