DEPENDENCE ON ASSOCIATION. 93 



the strength of association alone will retain and 

 hold the idea or action in its place in the series 

 for a long time after the originating stimulus has 

 disappeared. Thus the final movement of a finger, 

 in playing a well-practised trill on a piano, cannot 

 be dropped immediately. It requires a well-directed 

 effort and some practice to get rid of it. Neither 

 can an action be dropped easily from the middle 

 of such a series as we have been considering. 

 The association with the preceding and the suc- 

 ceeding members of the series, is so strong that 

 the middle member can be dropped out only with 

 great difficulty. Another characteristic of such 

 associated series is that the first portion of the 

 series is more strongly associated and more deeply 

 impressed in the nervous structure. This is readily 

 seen when the series has not been performed foi- 

 a long time and is weakened by disuse : the first 

 portion is more easily recalled, because, as the series 

 was learned, the first parts were more often repeated, 

 and the final parts were added on gradually one by 

 one. For instance, suppose we have a series of 

 four parts, and let number one be practised twelve 

 times before attempting the combination of one 

 and two ; then let the combination of one and two 

 be practised twelve times, and so on with one, two, 

 and three : we see that number one will have been 



