USES OF AUTOMATIC NER VE- CENTRES. 309 



membrane; these arouse a reflex centre of swallowing, 

 which sends out nervous impulses to the swallowing mus- 

 cles, and the food is sent on into the gullet whether we wish 

 it or not. Sneezing when something irritates the mucous 

 membrane of the nose, and coughing where some foreign 

 mass enters the larynx, are other instances of reflex actions. 



The Use of Automatic and Reflex Centres is to relieve 

 the thinking centres of the vast amount of work which 

 would be thrown upon them if every action of the body 

 each moment had to be planned and willed. Were not the 

 unconscious regulating nerve-centres always at work the 

 mind would be overburdened by the mass of business which 

 it would have to look after every minute. No time would 

 be left for intellectual development if we had to think 

 about and to will each heart-beat, each inspiration and ex- 

 piration, and the swallowing of each mouthful of food. 

 Moreover, during sleep, so necessary for the rest and repair 

 of the psychic centres, the automatic and reflex centres 

 carry on the actions essential for the nutrition of the body 

 and the maintenance of life. If we had to reason concern- 

 ing each beat of the heart and decide if it was time for it 

 to occur and what force it should have, and then to make up 

 our minds whether to will it or not, we could never sleep. 



Habits are Acquired Reflex Actions, distinguished from 

 primary or those born with us, such as sneezing, coughing, 

 and winking. Every time a nerve-centre acts in a given way 

 it tends to more easily act in that manner again; as a result 



Give other examples of reflex actions. 



What is the main use of th<3 automatic and reflex nerve-centres? 

 What would result if the unconscious nerve-centres were not always 

 at work? 



What are habits? What happens when a nerve-centre acts in a 

 given manner? What is the result? 



