John Hughlings-Jackson: a sesquicentennial tribute.

One hundred and fifty years have elapsed since the birth of John Hughlings-Jackson, a pivotal figure in the development of clinical neuroscience. In this review the origin of Jackson's postulate of a hierarchical organisation of function in the nervous system is described in the context of his education and his contacts with contemporaries, both in his clinical practice at The London Hospital and at the National Hospital, Queen Square, and in relation to the evolutionary approach to the organisation and ideas on biology and society set out by the philosopher Herbert Spencer.