JMS PearceHull, England Access to cerebrospinal fluid (CSF) in life as an aid to diagnosis proved impossible until lumbar puncture. Galen of Pergamon (AD 130–200) failed to recognize CSF; he described a vaporous, not aqueous, humor that he called περιττώματα (residues) in the cerebral ventricles. Cerebrospinal fluid in the ventricles was probably first shown by…