The second principle is not 浙医一院 obvious and may seem counterintuitive The spinal fluid is produced at a constant rate(15-20 mL/hr) largely by the choroid plexus of the ventricles by an energy- dependent, physicochemical pI rocess。The second principle is not obvious and may seem counterintuitive: The spinal fluid is produced at a constant rate (∼15-20 mL/hr) largely by the choroid plexus of the ventricles by an energydependent, physicochemical process