408 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Table III. — EUctric aiimulation; ])omts A, B, C,andD. J and C ohserrers. 2,400 reactions. 



The averages of all tlie times for the two observers were almost exactly the same — 127.4 c 

 for J and 1L'8.;5 ff for 0. The departures from the average for the ditiereiit points coiiseiiueiitly 

 represent real difiereuces iu the nature of the process. These are for J on A — .J.S (7 B, — 2.9 a; 

 D + 0.8 o- and C + 8 c; for C on D, -So" A - 3.1 g; C + 2..-> c and B + 8.7 a. The reaction-times 

 are without exception inversely proportional to the intensity of the sensation. It is consc'iuently 

 impossible to draw any conclusion from the experiments concerning the velocity of the nervous, 

 impulse in the sensory nerve. 



In order to accomplisli this it would at all events be necessary to nialce the sensations- 

 subjectively alike in intensity, or to make a correction for intensity. In order to study the relation 

 between reaction time and intensity we made reactions on the four points on the arm with three 

 intensities of shock. The strongest was nearly the same as in the preceding experiments, but a- 

 little stronger so as to be somewhat jiainful for J. Thp weakest was barely iierceptible for C on 

 the point B. The same physical stimulus produced much greater physiological effects on J than 

 on C The middle intensity was intended to be midway between the strongest and weakest, but 

 after the experiments had been made it was thought to have been too weak. In Table lY the 

 results are given of one hundred reactions on each of the four points and with each of the tliree' 

 intensities. 



T.^BLE IV. — Etectrtc aliniiihUioii; strontj, mcdiinHf and .weak shocks. J'o'nils ,1. />, C, und IK 



^,400 reactions. 



J and (' ohscrvcrs. 



The table shows that the reaction-time was shorter when the shock was stronger. The- 

 decrease in time, when the intensity was increased from weak to medium, was for J 7.1 a, for 

 12.7 ff; from medium to strong, for J 1.3 ff and for C 26.2 ex. The difference in the case of the two 

 observers is due to the fact that tlie subjective differences were greater for C, in whose ease the- 

 weakest shock was barely perceptible on B. The difference in the time of reaction for 0, wlien the- 

 shock was barely iierceptible (on B) and when it was very strong (on D), was 65.2 a: The average- 

 times were nearly the same on A and D, for J 1.7 a shorter on D, for C 0.8 <7 longer. The shock 

 seemed stronger on I). We must consequently conclude that the time of transmission iu tlie nerve 

 from A to D is counterbalanced by a shorter central time in the case of A, and that this sliorter- 

 central time is not due to difference m intensitv, but to difference in the distribution of hbers in. 



