THE NERVOUS SYSTEM. 33 



nervous system, for the reason that it seems to have 

 control of some of the most vital operations of the 

 body. When it is injured, .the breathing muscles 

 fail to act, which, of course, means instant death. 

 Here (150) we see the spinal cord continued down- 

 ward. Now we will turn again to the nervous plate of 

 the Aid, where the whole of this great nervous 

 cord is shown with its numerous branches of nerves. 



The nerves are composed of the same 

 TheXerves. ji i_ mi -i 



substance as the brain. Iney are sil- 

 very threads which branch out from the brain and 

 spinal cord and are distributed to all parts of the 

 body. Twelve pairs pass out through openings of 

 the cranium. These are called cranial nerves. 

 Thirty-one pairs pass out from the spinal cord 

 through openings of the back-bone, as shown on the 

 plate. These are called spinal nerves. The cranial 

 nerves go to the eye, ear, nose, tongue and other 

 important organs. The spinal nerves go to the 

 arms, trunk and legs. 



Besides the nerves which branch out from the 

 brain and spinal cord, there is, on each side of the 

 back-bone, a chain of nerve centers little bits of 

 brains, as it were running down through the body. 

 From these small nerve knots, delicate nerves run out, 

 some to the heart, lungs and stomach, and others to 

 the blood-vessels and to the cranial and spinal 

 nerves. So all the important organs of the body are, 

 in this way, connected with each other and with the 

 brain. This figure (The Sympathetic System) shows, 



