 The central nervous system C and S is a part of the nervous system consisting of the brain and spinal cord. The central nervous system is so named because it integrates information it receives from, and coordinates and influences the activity of, all parts of the bodies of bilaterally symmetric animals. That is, all multicellular animals accept sponges and radially symmetric animals such as jellyfish. And it contains the majority of the nervous system. Many consider the retina and the optic nerve cranial nerve II as well as the alfactory nerves cranial nerve I and alfactory epithelium as parts of the CNS, synapsing directly on brain tissue without intermediate ganglia. As such, the alfactory epithelium is the only central nervous tissue in direct contact with the environment, which opens up for therapeutic treatments. The CNS is contained within the dorsal body cavity, with the brain housed in the cranial cavity and the spinal cord in the spinal pine bale. In vertebrates, the brain is protected by the skull, while the spinal cord is protected by the vertebrae. The brain and spinal cord are both enclosed in the myonges. In central nervous systems, the interneuronal space is filled with a large amount of supporting non-nervous cells called neurodial cells.