Light micrograph of a transverse section through the human spinal cord. Grey matter, consisting of unmyelinated nerve cells, forms the butterfly- shaped internal core of the spinal cord (seen here as the golden brown region at right). Outside this is the white matter (the light brown region at left) made up of myelinated nerve fibre bundles, or tracts. These carry information from the brain to the spinal column and vice versa. The spinal cord is wrapped in three layers of membrane, the meninges, not visible here. The cord extends from the brainstem to the level of the second lumbar vertebra. Magnification: x40 at 35mm size.