Scientists have speculated as to the nature of cerebrospinal fluid (CSF) - "the third circulation" or "vital spirit" for centuries. Just what is this mysterious bathing solution of the central nervous system? Is it a vehicle of transport for an "animal spirit" directing all our activities, as thought by Galen (Singer, 1956) or but a "modified tap water" (Halliburton, 1917)? With the advent of lumbar puncture, cerebrospinal fluid has become a readily available and important means of studying disease affecting the nervous system. In recent years, many sophisticated tools including com puter...