Touch: tactile sensation received by the skin, enabling the organism to detect objects or substances in contact with the body. End organs (nerve endings) in the skin convey the impression to the brain. Touch sensitivity varies in different parts of the body, depending on the number of end organs present in any one area. The tip of the tongue, lips, and fingertips are three of the most sensitive areas, the back and parts of the limbs the least so. The sense of touch is very closely related to the other four sensations received by the skin: pain, pressure, heat, and cold. There is a specific kind of sensory receptor for each of the five so-called cutaneous senses. For example, light-touch receptors convey only the sensation that an object is in contact with the body, while pressure receptors convey the force, or degree, of contact. The blind learn to read by the Braille system by making use of the sensitivity to touch of the fingertips.