294 



ADVANCED PHYSIOLOGY 



Surf ace- : 



THE CEREBRUM AND ITS FUNCTIONS 



The cerebrum is by far the largest and most important 

 part of the brain and is the real center of thinking, perceiving, 

 willing and indeed of consciousness. Its 

 primary activities are carried on by the nerve 

 cells located in the gray matter or cortex. 

 The most important experiences in our lives 

 are carried on through the activities of these 

 cells. It is much easier to think of cells of 

 protoplasm as giving rise to materials like 

 saliva or bile, than to imagine them making 

 thoughts. The former process is called se- 

 cretion; but shall we speak of the cells of the 

 brain as " secreting" or " making" thoughts, 

 or as "containing" memories, which may be 

 drawn on at will? We do not know; but we 

 do know that it is these cells that are the real 

 thinking part of the body. 



Figure 149 shows a section of the cortex. 

 It will be noticed that the cells are of several 

 different kinds and shapes, though very few 

 are round and nearly all have several angles 

 or corners from which extend and branch 

 thread-like outgrowths, called dendrites; Fig. 

 11, page 18). There is always one process 

 from each cell that extends much farther 

 than the others and finally ends, either near 

 dendrites of other cells, or else passes down the 

 spinal cord. This long outgrowth becomes the 

 central axis of a nerve fibre, over which 

 messages are either sent or received as the case 

 may be, sometimes for as great a distance as 

 two or three feet. Further description of these 

 nerve cells will be made later (page 310). 



F i G. 149. A 



SECTION O F 

 THE CEREBRAL 

 CORTEX 

 To show the nu- 

 merous cells that 

 it contains. The 

 surface of the 

 brain is at the 

 top and the white 

 matter would be 

 at the bottom of 

 the figure. 



