Writing in 1587, Giulio Cesare Aranzi (1530–1589) describes a structure ‘continuous with the vaulted body or tortoise (fornix) which has an uneven or bent form that resembles the appearance of a hippocampus, that is a sea-horse’ ( De humano foetu liber tertio editus, ac recognitus. Euisdem anatomicarum observationum liber , Chapter 3, pp. 45). Paul Broca (1824–1880) and Ludwig Edinger (1855–1918) traced direct connections of the olfactory tract into the hippocampus. But in Trabajos del Laboratorio de Investigaciones Biologicas del la Universidad de Madrid (Tomo 1: 1901–02; 1–227. Translated as Studies on the Cerebral Cortex by Lisbeth M Kraft, London 1955), Santiago Ramon y Cajal (1852–1934) writes: ‘ … the acceptance of the existence of direct communicating pathways between the primary and secondary olfactory centres … and Ammon’s horn, the fascia dendata, septum lucidum, cingulated gyrus [and] suprasellar striae … finds its way into the field of anatomical investigation with the greatest of difficulties’. On the olfactory brain, Cajal and Camillo Golgi (1843–1926) were of one voice in declaring that there are no direct connections between the olfactory tract and the hippocampus. Forty-five years later, during the tenure of his Rockefeller Fellowship in the Department of Human Anatomy in Oxford (UK), while on leave from the Anatomical Department of the University of Oslo (Norway), Dr Brodal aims to challenge one of the several ‘conceptions [that] survive almost like proverbs and become proclaimed as long-established truths … show[ing] a remarkable tendency to outlast the tenability of the original observations on which they were based’. Specifically, why do neurologists support the ‘credundum’ that the hippocampus is an important olfactory centre? Comparative anatomists know that phylogenetically the hippocampus develops in association with the olfactory system and a strong sense of smell. (Sir David) Ferrier (1843–1928) has shown that electrical stimulation of the simian hippocampus …
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