Figure 38. Cerebrospinal fluid pathways. A, cerebral artery; C, cerebral vein; D, diploic vein; E, emissary vein; M, meningeal vein; 3 and 4, third and fourth ventricles. The lowermost part of the figure shows the caudal end of the spinal cord. lumbar puncture (L.P.) is performed in the lumbar cistern (below the termination of the spinal cord). With permission from R. O'Rahilly, "Basic Human Anatomy."