Cerebro-spinal Fluid

Cerebro-spinal Fluid is a clear, almost colourless, slightly alkaline fluid, closely resembling lymph in its composition, but containing less albumen. It is contained partly within the ventricular system of the brain, and in part in the loose connective tissue (subarachnoid meshwork), which lies between the Arachnoid and Pia Mater (q.v.), being continued from this latter situation along the lymphatic sheaths, which closely invest all the blood-vessels in the substance of the brain and spinal cord. The spaces which contain it communicate with the lymphatics of the head and of the nerves, and with the venous sinuses in the dura mater. Its main function, besides that of removing waste products, is to equalise the pressure within the skull. As the blood pressure increases that of the cerebro-spinal fluid diminishes, and vice versa. As the brain atrophies it is replaced by a proportionate increase in the fluid. In some dis- eases, such as acute and chronic Hydrocephalus (q.v.), it is greatly increased, and then it becomes a cause of atrophy of the brain. Its value as a water-cushion in diminishing the violence of shock from external injury has been already referred to at BRAIN. Cerebro-spinal means pertaining to the brain and spinal cord together, to the cerebro-spinal system. For Cerebro-spinal Meningitis, see MENINGITIS.