MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



409 



the brain. As in the case of iiiii)ulses from tlie arm and leg, we may bere conclude that impulses 

 from near the left hand lead more readily to a movement of the rijiht hand than do impulses from 

 the npper arm. This fact is itself interesting-, but nialces the deteriiiiuation of tiie velocity in the 

 plain nerve by this method diflicult or impossible. 



In addition to these experiments ou intensity we made reactions, in whicli the area of stimu- 

 lation was altered. The sensation from a larger area is more massive, from a smaller area more 

 piercing. It is consequently possible to make sensations from different parts of the body 

 (pialitatively more equal by using a smaller electrode on a point where the sensation is more 

 massive, owing to anatomical structure. The small electrode was 1 mm., the large electrode 10 

 mm. in diameter, the area being consequently one hundred times as great in the case of the larger 

 area. The electrodes were applied on tlie points A and I). 



Table V. — Electric, slimtilation; large and small areas. J and C observers. SOO reactions. 



For J the time was 0.1 a shorter with the large area, for C 5.7 a shorter. The difference in the 

 case of the two observers is due to the fact that for .J the small area on A was the strongest and 

 most painful of tlie four shoclis, whereas fijr C it was the weakest. Owing to the same fact, for J 

 the time was 5.8 a shorter on A, for C it was 3.5 a longer. 



It is evident that if the velocity of the impulse is to be measured by the difference in the 

 reaction-times, points on the skin should be chosen in which the sensations are as nearly as possible 

 alike, and the inreusity and area of the shocks should be adjusted to make the sensations, so far 

 as possible, exactly alike. We did not proceed with such experiments, however, partly because 

 it did not seem i)ossible to allow for the difference iu time of the cerebral reflex due to the place 

 of stimulation and partly because we found that better results could be obtained from mechanical 

 touches or blows. Before going ou, however, to describe our experiments on touch, we shall notice 

 some expei'iments, chiefly on electrical stimulation, which we made with a view to studying the 

 effects of attention directed to the point stimulated and the effects of the nature of the movement. 



Experiments have recently been published in Germany' which gave a much longer reaction 

 time when the attention was directed to the stimulus than when it was directed to the movement, 

 and Wundt holds that in the former case the time is longer because the stimulus must be i)erceived 

 before the movement is made. This might pro\'e a complication in our experiments, as when the 

 shock was shifted from place to place the attention would be naturally directed to it, more especi- 

 ally as it was somewhat painful. We made, consequently, reactions in which the attention was 

 directed alternately to the stimulus and the movement, and used sounds as well as electrical 

 shocks. The sound was a tolerably loud noise made by the single click of a Morse sounder, a 

 strong current being used. 



T.viiLE VI. — Motor and sensory reactions on electrical stimulation and sound. C, J, and D observers. 1,000 reactions. 



' By Lauge, Miinsterberg, Martius, Killpe, and Titcliener. 



