86 



PSYCHOLOGY. 



sliadowing the reign of a newer and colder race of gods. 

 We shall take up the various operations measured, each in 

 the chapter to which it more naturally pertains. I may 

 say, however, immediately, that the phrase ' velocity of 

 thought' is misleading, for it is by no means clear in any 

 of the cases what jjarticular act of thought occurs during 

 the time which is measured. * Velocity of nerve-action ' is 

 liable to the same criticism, for in most cases we do not know 

 what particular nerve-processes occur. What the times 

 in question really represent is the total duration of certain 

 reactions upon stimuli. Certain of the conditions of the reac- 

 tion are prepared beforehand ; they consist in the assump- 

 tion of those motor and sensory tensions which we name 

 the expectant state. Just what happens during the actual 

 time occupied by the reaction (in other words, just what 

 is added to the pre-existent tensions to produce the actual 

 discharge) is not made out at present, either from the 

 neural or from the mental point of view. 



The method is essentially the same in all these investiga- 

 tions. A signal of some sort is communicated to the subject, 

 and at the same instant records itself on a time-register- 

 ing apparatus. The subject then makes a muscular move- 

 ment of some sort, which is the ' reaction,' and which also 

 records itself automatically. The time found to have elapsed 

 between the two records is the total time of that observation. 

 The time-registeidng instruments are of various types. 



Signal. 



Reaction. 



W\/\/wv\y\y\AAAA/w\yv\AAA/^ 



Reaction- line 

 Time-line. 



Fig. 21. 



One type is that of the revolving drum covered with smoLed 

 paper, on which one electric pen traces a line which the 

 signal breaks and the -reaction ' draws again ; whilst another 

 electric pen (connected with a pendulum or a rod of metal 

 vibrating at a known rate) traces alongside of the former 



