ASSOCIATION. 581 



fome day clear the matter up ; possibly neural laws will 

 not suffice, and we shall need to invoke a dynamic reaction 

 of the form of consciousness upon its content. But into 

 this we cannot enter now. 



To sum up, then, we see that the difference between the 

 three hinds of association reduces itself to a simple difference in 

 the amount of that portion of the nerve-tract supporting the 

 going thought which is operative in calling up the thought ivhich 

 comes. But the modus operandi of this active part is the 

 same, be it large or be it small. The items constituting 

 the coming object waken in every instance because theii 

 nerve-tracts once were excited continuously with those oi 

 the going object or its operative part. This ultimate physio- 

 logical law of habit among the neural elements is what runs 

 the train. The direction of its course and the form of its 

 transitions, whether redintegrative, associative, or similar, 

 are due to unknown regulative or determinative conditions 

 which accomplish their effect by opening this switch and 

 closing that J setting the engine sometimes at half-speed, 

 and coupling or uncoupling cars. 



This last figure of speech, into which I have glided un- 

 wittingly, affords itself an excellent instance of association 

 by similarity. I was thinking of the deflections of the 

 course of ideas. Now, from Hobbes's time downward, 

 English writers have been fond of speaking of the train of 

 our representations. This word happened to stand out in 

 the midst of my complex thought Avith peculiarly sharp 

 accentuation, and to surround itself with numerous details 

 of railroad imagery. Only such details became clear, how- 

 ever, as had their nerve-tracts besieged by a double set of 

 influences — those from train on the one hand, and those from 

 the movement of thought en the other. It may possibly be 

 that the prepotency of the suggestions of the word train at 

 this moment were due to the recent excitation of the rail- 

 road brain-tract by the instance chosen a few pages back of 

 a railroad king playing foot-ball with the stock-market. 



It is apparent from such an example how inextricably 

 complex are all the contributory factors whose resultant is 

 the line of our reverie. It would be folly in most cases to 



