34 ELEMENTARY PHYSIOLOGY. 



beautifully, this wonderful nervous connection. The 

 interesting object of this arrangement which is 

 called the sympathetic nervous system we shall 

 soon learn. 



There are three kinds of nervous action. 

 Action!** We will first consider the relation between 



mind, brain and nerve. The nervous 

 system is very much like a telegraph system. The 

 mind has been called the operator, the brain and 

 spinal cord the sending or receiving offices or 

 instruments, and the nerves the wires or lines 

 running to all parts of the body. The comparison 

 is very apt, indeed. One set of nerves runs from 

 the brain or spinal cord to the muscles, so that every 

 muscular fiber is in direct communication with head- 

 quarters. Now, wherever a muscle is to act, every 

 fiber of it, in some mysterious way, gets a message 

 over its nerve line, from the nervous capital, 

 directing it precisely how much to contract or relax. 

 For example, you make up your mind to close your 

 eyes. The order is sent out over the nerve lines 

 which go to the fibers of the circular muscle which 

 we have found to lie around the eye, and promptly 

 the eyelids close. The nerves which carry messages 

 to the muscles are called nerves of motion. Another 

 set of nerves are called nerves of feeling. They 

 carry impressions from the body to the brain. These 

 nerves are distributed so thickly near the surface of 

 the body, in the skin, that it would be almost impos- 

 sible to find a point on the body where the prick of 



