The works and thoughts of Santiago Ramn y Cajal in a faithful rendition of the original Spanish version, with additional facts contained in the French translation, both of which are currently quoted around 200 times each year in the scientific literature. This is the only authorized English translation and makes use of uniform nomenclature according to contemporary scientific English. Most of the illustrations are reproductions of Cajal's original art work, with cross references to the figure numbers of the Spanish and French versions, while the taxonomic glossary uses current scientific names, and their colloquial English counterparts.