STRUCTURE AND FUNCTIONS OF THE CEREBRUM 155 



which originally entered the nervous system by way of the re- 

 ceptors, and which have since been combined in various ways, 

 and the resulting associations stored as memories. Voluntary acts 

 are, therefore, the completion of reflexes. 



The Usefulness of Associative Memory Depends on its Orderli- 

 ness. It is perfectly obvious that associations to be of value must 

 be formed from related impressions or related concepts. We 

 know that our brains normally form associations in this orderly 

 way. How the brain is guided in its selection of material for 

 making associations so as to include what is relevant and exclude 

 the rest is quite beyond our knowledge or even imagination. That 

 in the highly complex associative processes which we call think- 

 ing there may be a conscious selection or rejection of memories 

 we know from our own experience. 



It is true, of course, that the brain, being an imperfect instru- 

 ment, often makes mistakes and forms associations that instead 

 of being useful give rise to harmful activities. The resulting 

 disaster, through the additional knowledge it affords, may enable 

 the brain to form correct associations next time. Thus we profit 

 by our mistakes. 



The Interaction of Associative Memories. Inhibition. The hu- 

 man brain acquires in the course of years such a wealth of associa- 

 tive memories, based upon so many phases of experience, that the 

 determination of the conduct to be employed in any particular 

 situation becomes often a matter of much difficulty. One set of 

 memories point toward one course and another set toward quite 

 the opposite course. When this happens it is necessary to call 

 in more and more remote considerations until the balance tips 

 unmistakably in one way or the other. When even this pro- 

 cedure fails to be decisive, or when the mind wishes to avoid the 

 labor of deciding by this method recourse is often had to a se- 

 lective external stimulus. Deciding a course of action by the 

 flip of a coin is a case in point. 



Associative memories also come into conflict when immediate 

 considerations point toward one course and remote considerations 

 toward a different one. Associative memories are classified by 

 placing those of remote bearing higher than those of immediate 

 bearing. Highest of all, because most remote, are abstract con- 

 ceptions of right and wrong; conceptions of altruism, care for 



