2OO THE SYMPATHETIC NERVOUS SYSTEM. 



If the nerves of the leg be not injured at all, but the 

 spinal cord be cut or seriously diseased above the place 

 where they join it, the leg loses all feeling and has its 

 muscles paralyzed just as if its nerves themselves were 

 cut. The reason of this is tha* ,ie nerve-fibres which 

 run up the spinal cord to the cerebrum and cause feel- 

 ing, and those which run down from the cerebrum to 

 the leg and make its muscles obey the will, have been 

 divided. The spinal cord, in addition to being a centre 

 itself for many reflex movements, is a sort of nerve : it 

 affords a path for many nerve-fibres which run between 

 the cerebrum and most parts of the body. 



11. The Sympathetic Nervous System. In addition to 

 the great system of nerves we have been studying, which 

 branches out from the brain and spinal cord, and then 

 divides and divides until it reaches every organ, and 

 covers the surface of the body as closely as the capilla- 

 ries (p. 147) do, so that the prick of a pin-point must 

 touch one of the little branches in addition to this great 

 set of cerebro- spinal nerves there is another, called the 

 sympathetic system. The nerves of the sympathetic system 

 are not spread through the skin or concerned in the 

 sense of touch; nor are they subject to the will and con- 

 cerned in producing voluntary movements. But they 

 go to the lungs, and the heart, and the liver, and the 

 stomach and intestines, and to the involuntary muscles 

 (p. 42). They do not run direct to the brain and spinal 

 cord, but first to certain smaller centres, lying principally 



cord is cut above where the nerves of the leg enter it ? Why ? What 

 is the spinal cord in addition to being a centre? 



ii. What is said of the nerves connected with brain and spinal 

 cord ? Of the nerves of the sympathetic system ? What is a gangli- 

 on ? Why so named ? What is the sympathetic system ? Its duties ? 



