The document discusses the history of understanding of physiological influences on the brain and nervous system from ancient times through the 19th century. It covers early ideas about the brain and localization of functions from Greek doctors through Renaissance thinkers like Descartes. Key figures like Bell, Magendie, Muller, Helmholtz contributed to understanding of nerve function and visual perception. Phrenology led to the idea of localization of mental functions in the brain, while Flourens and others showed specific brain areas are involved in different functions. Broca and Wernicke identified language centers, and Weber and Fechner founded the field of psychophysics through quantitative studies of sensation and perception.