14 THE ELEMENTARY NERVOUS SYSTEM 



the higher animals, it was a long time before this system 

 was recognized as the exclusive seat of the most striking 

 characteristic of man, his mental life. Only gradually 

 was it discovered that his conscious states represent the 

 action of a single system of organs, the nervous system, 

 as contrasted with the rest of his body. 



To the ancients this conscious life, whose chief at- 

 tribute is personality, seemed to permeate the whole 

 human frame. In fact, Aristotle, who was such an ac- 

 curate observer and profound thinker in so many fields of 

 biology, denied positively that the brain was in any direct 

 way concerned with sensation and declared the heart to 

 be the sensorium commune for the whole body. To Galen 

 is ascribed the belief that the brain is the seat of the ra- 

 tional soul, the heart the location of courage and fear, and 

 the liver that of love. The distribution of the elements 

 of personality over the physical body finds its expression 

 in the common speech of to-day, particularly in relation 

 to the heart, which is widely accepted by the popular mind 

 as the seat of the more tender emotions. Although this 

 opinion may commonly imply a certain amount of poetic 

 license, it is quite certain that many an untrained person 

 holds even at the present time to a literal interpretation 

 of the ancient view of the location of sensations. The 

 pain of a pin nrick is commonlv believed by many persons 

 to be where the pin enters the skin. To thorn nothing 

 seems more obvious and certain than that the punctured 

 spot is the seat of the pain, and any attempt to change 

 their views on this point will usually be regarded by them 

 with suspicion and mistrust, for it seems contrary to 

 common sense. 



Nevertheless, it is well known that if a nerve distrib- 

 uted to a given area of skin is cut at some distance from 



