Examination of the cerebrospinal fluid (CSF) for diseases of the nervous system began with Quincke with his reports in 1872 (34a) and 1891 (34) (see Chapter 1). He popularized the use of spinal puncture (spinal tap) in the lumbar region (lumbar puncture; LP) mainly for the diagnosis and treatment of hydrocephalus. However, one of his cases did have an intracranial bleed. He measured the opening and closing CSF pressures, the amount removed, the specific gravity, and the protein concentration. This set the stage for confirmation of subarachnoid hemorrhage, a diagnosis presently made by visual CSF examination and, more recently, computerized tomography.