[L. nervus.] All the organs of the body are connected by nerves - each a bundle of nerve fibres enclosed in a special sheath - either with a great mass of nervous matter called the brain, or with a long thick nerve called the spinal cord, which runs down the centre of the back-bone. Delicate white threads or nerves pass from the brain through little holes in the skull to the ears, eyes, nose, mouth, etc. Long but very fine nerves extend from the spinal cord to all parts of the body. By the nerves sensations or feelings are transmitted to the brain. If the nerves going from the tip of a finger to the brain are cut, we can no longer feel anything with that finger. Again, if any part of the skin is touched, the sensation passes along a nerve to the spinal cord, and then up that great nerve trunk to the brain. But the nervous system does more than merely receive sensations. All the movements of the muscles are directed and governed by the nerves, and similarly the action of all the other organs of the body is under the control of the nervous system.