On the origin of the term decussatio pyramidum.

There is no consensus regarding the origin of the term decussatio pyramidum. Various anatomists of the past are honored by modern scholars, for example, Vieussens, Reil, and Collins. However, contralateral effects of brain lesions were already mentioned in Hippocratic treatises. Aretaeus of Cappadocia assumed that the anatomical reason for this phenomenon is the interchange of the nerves and called it chiasmos. This opinion was discussed in modern times and the anatomists used the term decussatio nervorum. The authorship of the first demonstration of decussatio pyramidum is given to Mistichelli (1709) and Petit (1710), but neither the term decussatio nor any of its vernacular forms are present in their work. A milestone in the history of the term is the Mémoire of Gall and Spurzheim presented to the Institut de France in 1808. In the French printed form of the Mémoire (1809), the word combination décussation des pyramides was used for the first time in anatomical literature.