Francois Magendie was a French experimental physiologist. In 1822, he demonstrated that the anterior roots of the spinal nerves are motor and the posterior roots of the spinal nerves are sensory. But Magendie was also a vitalist: he believed that the "life force" or "vital force" was essential both to health and recovery from disease. Magendie opposed surgical and obstetric anaesthesia because they weakened this hypothetical force, reducing the patient "to a corpse". Pain, Magendie declared, was "one of the prime movers of life".