and the long journey toward a scientific understanding of the

physiological nature of pain had begun.

 Modern approaches to the nature of the pain experience come from

 many disciplines. The gate theory proposed by Melzack and Dennis (1978)

 is perhaps the best known and most popular of the physiological

 approaches. Gate control theorists only attempt to explain the activity

 of the nervous system when pain is experienced. Gate control theory

 proposes that "neural mechanisms in the dorsal horns of the spinal cord

 act like a gate that can increase or decrease the flow of nerve impulses

 from peripheral fibers to the spinal cord cells that project to the

 brain" (Melzak & Dennis, 1978, p. 2). This adjustment of the nerve

 impulses takes place before injury or somatic input invokes pain

 perception and response. According to the theory, large fiber inputs

 close the gate, and small fiber inputs open the gate. The mechanism for

 the inhibition and facilitation is unknown. Since it is now known that

 all dorsal horn cells are under the control of fibers that descend from

 the brain, it is believed that descending influences such as motiva-

 tional drive and cognitive evaluative activities will also affect the

 gate. When the output of the spinal cord transmission exceeds a

 critical level, the individual experiences pain. "The complex sequences

 of behavior that characterize pain are determined by sensory, motiva-

 tional, and cognitive processes that act on motor mechanisms" (p. 12).

 Motor mechanisms are "all of the brain areas that contribute to overt

 behavioral response patterns" (Melzak & Dennis, 1978, p. 12).

 The affective influence espoused by the ancients seems consistent

with current research of scientists such as Melzack and Dennis.