ANALGESIA is the name given to the loss of the sensation of pain, and is due to an interruption of the nervous pathway between skin and brain. Different forms of sensation from one area of skin, such as touch, temperature, and pain, travel to the spinal cord by different nerve fibres in the same nerve bundle. Hence any injury or disease affecting such a nerve would abolish all forms of sensation in the area supplied by it. However, when the sensory nerves reach the spinal cord their fibres separate and pursue different courses on their way upward to the brain. Thus it is possible for certain forms of sensation to be lost, while others are preserved, in diseases which affect only certain areas in the spinal cord. Since the sensations of pain and temperature travel the same path, they are usually lost together. Diseases of the cord which may cause analgesia without loss of the sensation of touch are tabes dorsalis, syringomyelia and tumours of the cord. Analgesia may also be a manifestation of hysteria.