THE NERVOUS SYSTEM 119 



flex or adduct the thigh or extend the knee, receive 

 their impulses through the lumbar plexus. 



The sacral and coccygeal nerves supply motor and 

 sensory fibers to the external genitals, the hip, back of 

 the thigh and all of the leg and foot, except the inner 

 side of these parts which receive their supply from the 

 lumbar plexus. 



THE AUTONOMIC SYSTEM 



The chain of ganglia and nerve fibers which lies on 

 each side of the vertebral column is usually called sym- 

 pathetic, because it was formerly supposed that sympa- 

 thetic or reflex impulses w r ere carried by it. The more 

 recent name, autonomic is derived from words meaning 

 "a law r unto itself," and is appropriate because this sys- 

 tem of nerves is entirely independent of the conscious 

 will ; i.e., is independent of that portion of the brain 

 which consciously directs. That some of these fibers are 

 connected with the brain through cranial nerves is ap- 

 parent and all are under the control of some portion of 

 the brain ; but that only means that there are brain areas 

 over which man exercises no control. Some of the gan- 

 glia of this system are found in the skull and are con- 

 nected with cranial nerves, notably the ciliary which 

 gives branches to the iris or pupil ; but the larger num- 

 ber lie along the spinal column and are connected with 

 nearby spinal nerves by two roots a white (medul- 

 lated) fiber which runs from nerve to ganglion and a 

 gray (nonmedullated) fiber which passes from ganglion 

 to nerve which afterwards distributes it to nonstriated 

 muscle fiber. Through the spinal and cranial nerves, 

 the sympathetic ganglia are connected with the central 

 nervous system in these regions (1) through the third 

 nerve with the midbrain, (2) through the seventh, ninth, 



