Charles-Édouard Brown-Séquard was a French physiologist and neurologist born in 1817. He is best known for his research on the nervous system and hormone functions. Brown-Séquard's work laid the foundation for understanding the role of the endocrine system in regulating bodily functions. In 1889, he famously conducted an experiment involving the injection of testicular extracts, claiming it rejuvenated his energy and vitality. This led to the development of hormone therapy, influencing future medical practices. Brown-Séquard's contributions to science have had a lasting impact on both neurology and endocrinology.