THE HIGHER ORGANISMS 177 



stimulating a motor centre in the spinal cord by which 

 an impulse was sent out to the muscles of the arm 

 which was quickly drawn away by their contraction. 

 In the meantime, the metal impression is being rapidly 

 passed about from cell group to cell group until it arrives 

 at a group of cells formerly stimulated in the same 

 manner which now feebly revive the sensation, as one 

 produced by a sharp object, and then to another group 

 of cells which recall the scissors, and from these to others 

 by which you become reminded of all that was done a 

 short time before and that you had left the scissors on 

 the table. The revived memories in these nerve cells 

 thus define themselves as thoughts, appearing at first 

 with such rapidity that they were very indistinct, but 

 becoming more and more clear as time is allowed for each 

 to arise, and as attention is directed toward it. Indeed, 

 if no means of interrupting the course of nervous dis- 

 charges arising in the brain in this manner is adopted, 

 and if no new and lively impression is received, the mem- 

 ories aroused in one group of cells after another continue 

 along in an orderly sequence, as, for example, self- 

 reproach for the carelessness shown in leaving the scissors 

 on the table, the advantage of blunt over sharp scissors 

 under such circumstances, the maternal admonition to 

 order and carefulness often expressed in early days, and 

 so on and on. 



If what may be regarded as a relatively simple act is 

 attended with such complex and correlated nervous 

 activity, how much greater it becomes when some 

 relatively complex act is considered. Thus from the 

 garden comes a stimulus that excites the nerve endings 

 in the mucous membrane of the nose and is transmitted 

 to the appropriate cells of the brain which receive the 

 impression as "perfume of rose. 11 When this impression 

 has been properly registered, you turn, look out of the 

 window and see receive a visual impression of a rose. 

 How beautiful! you must go and pick it. Impulses 

 now descend from the brain to the spinal cord, by which 



12 



