n, often cap 1st S  :  a deep fissure of the lateral aspect of each cerebral hemisphere that divides the temporal from the parietal and frontal lobes - called also fissure of Sylvius , lateral fissure , lateral sulcus 
 
Du•bois or  De Le Bo  Franois, or  Franz  ( Latin  Franciscus Sylvius ) (1614-1672), Dutch anatomist, physician, and chemist. As a professor of medicine at Leiden, Dubois was one of Europe's most celebrated teachers. He is considered by many the founder of the 17th-century school of iatrochemical medicine, a school that held that all the phenomena of life and disease are based on chemical action. This school sought to apply rationally the universal laws of chemistry and physics to medicine. He extensively investigated the anatomy of the brain, and in 1641 he discovered the deep cleft separating the temporal, frontal, and parietal lobes of the brain. This cleft is now known as the sylvian fissure. He published his collected medical works in 1671.
 
 
 
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