PARTS OF THE NERVOUS SYSTEM OF MAN 201 



hunger nor fear, and is in every sense a machine which will perform 

 certain actions after certain stimulations. Its movements are 

 automatic. If we watch the movements of a frog which has the 

 brain uninjured in any way, we find that it acts spontaneously. It 

 tries to escape when caught. It feels hungry and seeks food. It 

 acts like a normal individual. 



Functions of the Parts of the Nervous System of Man. — There 

 are three types of functions over which the nervous system has 

 control. The first are the so-called autonomic activities of the 

 body. The heart beats and we breathe when we are asleep as well 

 as when we are awake. Our glands secrete and our kidney cells 

 excrete, all without any consciousness on our part. Nevertheless 

 the nervous system is always in control. 



A second kind of function is the kind of activity which once was 

 learned but now has become ^^ second nature " or habitual. If we 

 have well-regulated body machines, we get up in the morning, auto- 

 matically wash, clean our teeth, dress, go to the toilet, get our 

 breakfast, walk to school, even perform such complicated processes 

 as that of writing, without thinking about or directing the machine. 

 In these respects we have become creatures of habit. Certain acts 

 which once we learned consciously, have become automatic. 



Early in our lives we begin to gain a higher control of our body 

 activities. We then make conscious choice; we weigh one course 

 of action against another and decide which is the best course for 

 us to follow — in short, we think. This is the highest tj^e of 

 conscious activity. 



Localization of Functions. — In a general way, our central 

 nervous system is like that of the frog. The autonomic activities 

 are largely controlled outside the brain. The cerebellum largely 

 takes care of the habitual reflexes which we learned when growing 

 into childhood. The cerebrum has to do with a large number of 

 conscious activities. 



A large part of the area of the outer layer of the cerebrum seems 

 to be given over to some one of the different functions of speech, 

 hearing, sight, touch, and movements of body parts. The move- 

 ment of the smallest part of the body appears to have its definite 

 localized center in the cerebrum. In addition, certain areas have 

 to do with association, memory ; that is, the cells store memories 



