CHAPTER XXIII 



NERVOUS 

 REACTIONS 



Ancient idea of the human 

 nervous system. 



Present idea of the human 

 nervous system. 



What mental activities are learned and what are instinctive f What 

 is a habit f What is the best method for learning facts? 



When tropisms were discussed, the importance of stimuU was 

 stressed. As in plants and lower animals, it is a stimulus in a 

 higher animal that starts the nervous impulse wdiich results in a 

 typical reaction. This impulse may be any one of three types of 

 mental activities : (1) inborn automatic, (2) acquired automatic, 

 and (3) voluntary. 



Reflex activities. There are certain motions and acts that a 

 baby performs soon after it is born. These responses are simple 

 reflexes or inborn automatic activities. The child does not have to 

 learn or acquire them. Some of these responses may involve the 

 brain, while others are controlled only by the spinal cord. The 

 child comes into the world equipped with pre-formed connections 

 or tendencies to connections in his nervous system. In other words, 

 nervous pathways or patterns are already set up. A new-born 

 baby that has not learned to think will pull his foot away if 

 pricked with a pin. He will sneeze if his nostrils are tickled with a 

 feather, and will grasp a finger if it is placed on the palm of his tiny 

 hand. Each of these responses to the given stimulus is a reflex. 

 If a person swings one leg freely over the other and taps it just 



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