182 THE HUMAN BODY 



whom he has learned to know by these associated impres- 

 sions. 



Acts of association are supposed to be carried on within (lie 

 association areas of the cortex. We may picture the process in 

 the example cited above somewhat as follows: The impression of 

 the voice is stored in the auditory area; that of the appearance 

 of the face is in the visual area; both these sensory areas have 

 rich communications with neurons of the association areas. By 

 some means impulses from the sensory cells where these impres- 

 sions are stored meet in a cell of an association area. That cell 

 builds from these single related sense impressions, a composite, 

 which is stored in turn as a memory. As additional related in- 

 formation is gained the composite, or concept, is enlarged. 



The union of related impressions into concepts does not nec- 

 essarily involve loss or impairment of the fundamental impres- 

 sions themselves; the child in whose mind is a definite concept 

 of his mother retains also clear memories of her voice and her 

 face. The paths of communication between the cells where are 

 stored the primary sense impressions and those where the resulting 

 concepts are formed seem to remain always very easy of passage. 

 The sound of the mother's voice calls up the entire concept of the 

 mother with great clearness, even though years may have elapsed 

 since it was heard. 



Since concepts are stored as memories they may serve in their 

 turn as bases for more complex associations; these again by be- 

 coming memories may contribute to the associative process, and 

 so the complex structure of the mind is built up, resting at bot- 

 tom always upon primary sense impressions. 



The act of association is essentially one of combining related 

 memories; the formed associations become memories in their turn. 

 For these reasons the term associative memory is used as more 

 truly describing the nature of associative processes than the older 

 expression "the association of ideas." 



The use of a memory in forming one association does not inter- 

 fere with its use in the formation of others. This ability of the cere- 

 brum to use memories over and over again is a very valuable prop- 

 erty since it enables us to make the utmost of all our knowledge. 



Development of the Cortex. The increase in intellectual 

 power which accompanies the growth of the child is not the re- 



