<P> White matter in nonelderly adults is 1.7--3.6% blood . </P> <P> The other main component of the brain is grey matter (actually pinkish tan due to blood capillaries), which is composed of neurons . The substantia nigra is a third colored component found in the brain that appears darker due to higher levels of melanin in dopaminergic neurons than its nearby areas . Note that white matter can sometimes appear darker than grey matter on a microscope slide because of the type of stain used . Cerebral - and spinal white matter do not contain dendrites, neural cell bodies, or shorter axons, which can only be found in grey matter . </P> <P> White matter forms the bulk of the deep parts of the brain and the superficial parts of the spinal cord . Aggregates of gray matter such as the basal ganglia (caudate nucleus, putamen, globus pallidus, substantia nigra, subthalamic nucleus, nucleus accumbens) and brainstem nuclei (red nucleus, cranial nerve nuclei) are spread within the cerebral white matter . </P> <P> The cerebellum is structured in a similar manner as the cerebrum, with a superficial mantle of cerebellar cortex, deep cerebellar white matter (called the "arbor vitae") and aggregates of grey matter surrounded by deep cerebellar white matter (dentate nucleus, globose nucleus, emboliform nucleus, and fastigial nucleus). The fluid - filled cerebral ventricles (lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle) are also located deep within the cerebral white matter . </P>

Where is white matter located in spinal cord