Although it is known that Jacksonian epilepsy was first described by Bravais in 1827, some 40 years before Jackson began his work on the topic, little has been published on what Bravais wrote. Louis François Bravais (1801-1843) came from a French provincial family, which made a number of scientific, mainly botanical, contributions. In his Paris M.D. thesis, based on 25 instances of what he termed "hemiplegic epilepsy," Bravais described a set of unilateral epileptic seizure phenomena, including postseizure hemiparesis, very similar to those Jackson wrote about in 1870. However, Jackson accepted that the initially unilateral convulsive phenomena could spread to involve both sides of the body, whereas Bravais believed that this was incompatible with his entity, unless the generalization was a very rare event in the sufferer. Bravais in his account refused to go beyond descriptions of phenomena, whereas Jackson reasoned from the phenomena to a new concept of epileptogenesis, and also from them deduced that there must be localized representation of function in the cerebral cortex. Although Bravais had the priority, his work went largely unnoticed until Jackson's insights had made their impact on medical thinking.