Pain is a centrally integrated experience, the painful sensations being derived from impulses traversing specific pathways. According to Wolff and Hardy1 all fibers carrying impulses experienced as pain enter the spinal cord through the dorsal root ganglions. After entering the cord these impulses are conveyed across to the opposite side, where the pathways are localized in the anterolateral portion of the spinal cord. The fibers of the spinothalamic tract pass into the nucleus centralis posterior of the thalamus. The cortical projection from the nucleus centralis posterior is predominantly to the postcentral convolution. It is probable, according to Wolff and Hardy, that the brain structures involved in pain perception occur in both peripheral hemispheres in the region of the central fissure.
The function of the sense of pain is protective; it serves to warn of damage and urges the organism to defensive measures. There is a distinction between perception of