92 DEVELOPMENT AND HEREDITY. 



on top of one that they have already completed. 

 In the case of the musical performer, we know 

 that each individual action in the series must have 

 had its own separate stimulus before there arose 

 any subordinate nervous co-ordination, and also each 

 stimulus must have been practically independent of 

 the preceding action. It was only by the frequent 

 repetition of this series of stimuli in regular order 

 that the subordinate nervous co-ordination was 

 effected, so that finally the initial stimulus in the 

 series of stimuli is sufficient to guide the whole 

 series of actions. 



We know that if a certain train of ideas has 

 passed through our minds often enough to become 

 firmly associated, and if then a new stimulus shall 

 call up a new idea at the end of this train, then 

 there is a tendency for that new idea to be added on 

 when next the train of ideas shall repeat itself in 

 our minds. If the new stimulus should call up the 

 new idea at the end of the associated train of ideas 

 several times, then the new idea would remain in 

 that association a long time ; but if the new stimulus 

 should never again occur the new idea would 

 gradually fade away. We see how in this way the 

 final parts of an associated series may gradually 

 disappear when their originating stimuli wholly 

 disappear. But it is important here to notice that 



