Light micrograph of a section through part of the spinal cord, showing grey matter (dark pink, bottom) and white matter (light pink). The spinal cord is a downwards extension of the brain, and is responsible for relaying sensory and motor signals between the brain and the body. The grey matter consists of neuron (nerve cell) bodies, unmyelinated nerve fibres, support cells and capillaries. White matter consists solely of myelinated nerve fibres. Myelin is an insulating fatty layer that surrounds some nerve fibres. Its presence increase the speed at which nerve impulses travel. This tissue is from a cow. Magnification: x200 when printed at 15cm wide.