Histoire de l'anatomie du thalamus de l'antiquité à la fin du XIX^e siècle

The physicians of the Alexandrine school seem to have been able to follow the way of the optic nerves from the retina to the brain. It was very probable that they should discover the thalamus. Sadly, anatomic knowledge, deriving from the first scientific human dissection performed in history, was destroyed in the fire of the Alexandrine Library. When, in the second century A.D., Galen introduced the term thalamus opticus, he was describing the central part of the lateral ventricles of the brain. After Galen, an anatomy with philosophical inferences substituted an anatomy based on direct observation. At that time the purpose was to find the site of the soul. During the thirteen centuries following Galen, including the Byzantine epoch and the High Middle Ages, the knowledge of the anatomy of the central nervous system did not make any substantial progress. The deep location of the thalamus contributed, for a very long time, to make it invisible to the eyes of the anatomists. The modern approach to thalamic morphology began with the improving of the microscopy and histology techniques. In this context, K. F. Burdach proposed to separate the thalamus into distinct nuclei (1823) and later Jean Luys established the link between this anatomic subdivision and the idea of a functional specialisation (1865). Since then, a great amount of, often imprecise or contradictory, anatomic-functional data has accumulated rapidly. Throughout a critical synthesis of this growing knowledge and by the means of the modern nomenclature he introduced in 1877, Auguste Forel opened the way to the major development, which the subtle anatomy of the thalamus has undergone since the end of the nineteenth century.