Contributions to Neuroembryology of Santiago Ramon y Cajal (1852-1934) and Jorge F. Tello (1880-1958).

The contributions of Cajal to Neuroembryology are glossed with the help of a selection of images extracted from Cajals (1929) own synthesis of his neuroembryological output, laying emphasis on the persisting relevance and unsurpassed quality of many individual achievements and milestones he delivered on neurohistogenesis, practically throughout his career. Cajals theoretical background as regards embryology, morphology, comparative neuroanatomy and evolution is sketched at the beginning. The body of the review is divided into sections covering spinal cord, cerebellum, cortex, retina, sensory organs and muscular terminals, and astroglia. The deep and common-sensical conceptual analysis of neural histological variation during development performed by Cajal is highlighted at several points, as well as the places where he advanced genial conjectures that reached far forward in time, placing him still at the front of present day neuroembryological thinking. Some errors committed by Cajal are also commented upon. At one point (the retina), some of the present authors own observations with a Golgi method variant are presented, as they complement observations that Cajal left incomplete because of technical problems. The major neuroembryological works of Cajals pupil Jorge F.Tello are mentioned at the end.