the brain, nerves, and behavior to develop neurologic treatments. He described in great detail the structure of the brainstem, the cerebellum, the ventricles, and the cerebral hemispheres. Modern period The role of electricity in nerves was first observed in dissected frogs by Luigi Galvani, Lucia Galeazzi Galvani and Giovanni Aldini in the second half of the 18th century. In 1811, César Julien Jean Legallois defined a specific function of a brain region for the first time. He studied respiration in animal dissection and lesions, and found the center of respiration in the medulla oblongata. Between 1811 and 1824, Charles Bell and François Magendie discovered through dissection and vivisection that the ventral roots in spine transmit motor impulses and the posterior roots receive sensory input (Bell–Magendie law). In the 1820s, Jean Pierre Flourens pioneered the experimental method of carrying out localized lesions of the brain in animals describing their effects on motricity, sensibility and behavior. He concluded that the ablation of the cerebellum resulted in movements that “were not regular and coordinated". At mid century, Emil du Bois-Reymond, Johannes Peter Müller, and Hermann von Helmholtz showed neurons were electrically excitable and that their activity predictably affected the electrical state of adjacent neurons. In 1848, John Martyn Harlow described that Phineas Gage had his frontal lobe pierced by an iron tamping rod in a blasting accident. He became a case study in the connection between the prefrontal cortex and executive functions. In 1861, Paul Broca heard of a patient at the Bicêtre Hospital who had a 21-year progressive loss of speech and paralysis but neither a loss of comprehension nor mental function. Broca performed an autopsy and determined that the patient had a lesion in the frontal lobe in the left cerebral hemisphere. Broca published his findings from the autopsies of twelve patients in 1865. His work inspired others to perform careful autopsies with the aim of linking more brain regions to sensory and motor functions. Another French neurologist, Marc Dax, made similar observations a generation earlier. Broca's hypothesis was supported by Gustav Fritsch and Eduard Hitzig who discovered in 1870 that electrical stimulation of motor cortex caused involuntary muscular contractions of specific parts of a dog's body and by observations of epileptic patients conducted by John Hughlings Jackson, who correctly deduced in the 1870s the organization of the motor cortex by watching the progression of seizures through the body. Carl Wernicke