The problem of circulation of the cerebrospinal fluid is closely associated with other important but as yet unsettled problems pertaining to this fluid. Of these, the origin and the modes of its absorption will be considered in brief. According to the dominant teaching, the cerebrospinal fluid originates largely, if not exclusively, from the choroid plexuses of the two lateral third and fourth cerebral ventricles, from which it escapes mainly through the recesses of Luschka to the basal cisterns of the brain. From the cisterns, the fluid is supposed to run upward to the subarachnoid space of the cerebral convexity, where it is assumed to become absorbed by the villi of the arachnoid membrane and discharged into the venous sinuses of the dura. The cerebrospinal fluid is supposed to travel not only upward or cephalad but also caudad to the subarachnoid space and the central canal of the spinal cord. With