Csf is a clear colour less body fluid, bathes both brain & spinal cord. both the brain and spinal cord are covered by 3 protective members called meninges. The outer layer is called DURA MATTER and is composed of tough connective tissue. The middle layer is Arachnoid named for its spider web like appearance. The delicate inner most layer which is in direct contact with the brain and spinal cord is called PIA MATTER. Between the Arachnoid layer and the pia matter is a space called the SUBARACHNOID SPACE,which contains a clear colorless fluid called as CERBROSPINAL FLUID. 