In 1863, 2 years before Paul Broca published his heralded paper on the special role of the left hemisphere in speech, Gustave Dax sent a paper to the Académie de Médecine in Paris, France. His lengthy submission included an insightful memoir presumably written by his father Marc in 1836 and supportive material that he had collected himself. The present article examines the events leading to Gustave's 1863 submission to the Académie. It also presents an English translation of the negative response that this paper received and a translation of the short article that Gustave published in 1865. These materials help to show how cerebral dominance was first discovered, how it was made public, and how the first advocates of the concept were judged by their contemporaries.