126 APPENDIX I. 



the eye the slightest lapse of time between the 

 stimulation and the reflex contraction that John 

 Miiller had been induced to admit, as we have 

 pointed out, so enormous a velocity for the nervous 



agent.* 



Time required for Sensation and Volition in the 

 Brain. More recently researches of this kind have 

 been extended even to the time required for one of 

 the simplest operations of the brain, viz., the act of 

 sensation and subsequent volition. Dr. de Jaager, 

 in Professor Donders's laboratory, in Utrecht, first 

 repeated Dr. Schelske's experiment on the trans- 

 mission of sensation in the human body ; but with 

 this modification, that the shock could at will be 

 given either on the right or on the left side. In 

 one set of experiments, the person had to answer the 

 right-side shock with a spring-key in his right 

 hand, the left-side shock with a similar key in his 

 left hand ; and he knew, beforehand, on which side 

 he was going to be stimulated, and, therefore, would 

 have to answer. In another set of experiments the 

 side was not known beforehand, and the person, 

 after having received the shock, had first to consider 

 which side had been struck, and with which hand, 

 accordingly, he had to act. Now the mean result 

 in the first case was . . T! = *205 sec. 

 in the second T 2 = -272 



and the difference T^T^ =-067 

 * L. c., p. 583. 



