38 GENERAL STRUCTURE OF THE BODY. 



set in vibration and the vibrations being transmitted 

 along its length. Stimulation is produced by physical 

 injury, by chemical influence, by electricity, by heat, 

 and the message is always referred to the nerve termi- 

 nation. Thus, if the nerve at the elbow, over the 

 "crazy bone," is touched, a tingling is felt in the fingers 

 rather than at the point of pressure. A person who has 

 had an arm or leg amputated will frequently speak of 

 his fingers or toes on that side being cold, or complain 

 of pain in them, because the scar below the point of am- 

 putation tightens around the nerves and pinches them. 

 It is through the nerves that people get in touch with 

 the outer world and that they judge of size, weight, etc. 

 All careful adjustment of the muscles is under the 

 control of the nervous system. 



