The Contents of Ideas 161 



formed remains dormant until the elements 

 upon which they have been established are re- 

 excited, when their potential energy being set 

 free, is transmuted into nerve force and be- 

 comes manifest in a real image of the object 

 or of the movement which has caused the im- 

 pression. In order, therefore, that an idea 

 should assume the form of a real image of the 

 object or movement which has caused the 

 sensation, the elements on which the principal 

 features of the object have been established 

 must be re-stimulated by a similar or kindred 

 form of energy to that which produced the sen- 

 sation. Prof. Ziehen illustrates this point by 

 comparing the living matter of the impressed 

 nervous centres to the wheels, stars, etc., formed 

 out of gas-pipes as we see them in illumina- 

 tions. Unlit, they resemble the so-called latent 

 ideas; the charged materials are there, but a 

 spark must first light the gas that escapes from 

 many holes of the pipe in order that the latent 

 form may become a reality. 



The act of reading aloud illustrates our 

 meaning as regards the association of ideas in 

 operation. Energy derived from the concen- 



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