(n.) The delicate and highly vascular membrane immediately investing the brain and spinal cord.

arachnoid arbor vitae archipallium between brain brain stem cerebellar hemispheres cerebral cortex cerebrospinal fluid cerebrum convolution corpus callosum corpus striatum diencephalon dura mater endbrain fissure folia forebrain fornix frontal lobe glial cells globus pallidus gray matter gyrus hindbrain hippocampus hypothalamus lenticular nucleus limbic lobe little brain lobe mantle medulla oblongata meninges mesencephalon metencephalon midbrain myelencephalon neopallium occipital lobe optic chiasm pallium parietal lobe pia mater pineal body pituitary body pons reticular system rhombencephalon subthalamus telencephalon temporal lobe thalamus ventricle vermis white matter