Bauhaus-Universität Weimar

On reaction-times and the velocity of the nervous impulse
Cattell, J. McKeen and Dolley
Table II.—Reaction-times on electrical stimulation. D and J observers. 2,800 reactions. 
On A . 142.3 
do ......................... 120.2 
On A 119 
3.8 ' On B................... 
Electrodes 5 millimeters apart.. 
.. .do .. 120. 7 
4.7 .. 121.6 
4.1 ! . 117.7 
4. 7 
4.1 .......................... 
4. 5 
J ...... 
Electrodes 5 millimeters apart . 
On A . 137. 8 
G.8 j On B................... 
.. .do .. 121. 6 
4. 1 
On 11.. 122.4 
3. G 
On A . 116. 7 
____! On D................... 
.. do .. 122.7 
3.1 \ On D(5 olims resistance) 
The total time of ten reactions was measured, excepting in the first, second, third, and eighth sets, in which 
the reactions were measured singly. In these sets the mean variation of the single reactions from the series to 
which they belong was for J, 9.7 d; C, 8.7 6. 
The experiments do not discover any marked difference in the time of reaction when the 
shock was applied to the skin by electrodes 5 mm. apart, when the electrodes were on opposite 
sides of the limb, and when the current was conducted through the body to the foot. In the two 
sets in which the differences were directly compared the times were 1.6 ff and 4.3 ff shorter when 
the current passed through the limb than when it was applied simply to the skin. The sensation 
is more intense when the shock is applied through electrodes close together, and more massive when 
they are farther apart. This is a psychological distinction of some importance. One sensation 
would be greater than another either because it is more intense, the same nervous elements being 
more actively stimulated, or more massive, more nervous elements being stimulated. When the 
points A and B were stimulated—A being slightly the more distant from the brain—the reaction- 
time on A was the shorter, the differences being, for C, 0.0, 7.3, 5, 11.3, 12.6, 0.8, and —1.9 ff ; for 
J, 2 and 3.7 ff; on the average, 4.6 ff. The shorter time for the point D is due to the greater 
massiveness of the shock or the different nerve supply and cerebral connections. It is, con¬ 
sequently, evident that the reaction-time from the same physical stimulus applied to different 
points on the skin does not of necessity measure the velocity of the impulse in the plain nerve. 
When the shock was applied on A and D, at which points the quality of the shock was nearly 
the same, the times were nearly alike—116.7 ff and 117 a—and when 5 ohms resistance was placed 
in the current giving the shock on D (in order to make the intensities the same) the times were 
A 122.7 ff, and D 125 a. 
The experiments given in Table II were preliminary to a more thorough investigation of the 
variation in the reaction-time according to the point to which the stimulus was applied and its 
intensity. We took the four points in the arm marked (in fig. 7) A, B, C, and D, and made a large 
number of reactions on each of these points, the physical stimulus being always the same. As 
already stated, the sensation was not the same either in intensity or quality. The quality of 
sensation was much alike for A and D, massive as from a blow, and for 0 and B more piercing. 
This difference is accounted for by the intervening muscle in the case of A and D and the muscular 
contractions which followed stimulation of these points. The intensity of sensation was not, 
however, alike for A and 1) and for B and C, respectively. A further and unexpected complication 
occurred, the relative intensities not being the same for the two observers who took part in the 
experiments. In the case of C the order of intensity was D, A, C, B, the differences between D 
and A and between C and B being large. A and 0 were nearly alike in intensity, but the difference 
in quality made it difficult to compare the intensities. The shock from eight cells in pairs on D was 
nearly the same as from twenty-eight cells on A; that from fourteen cells on A or C was nearly the 
same as from twenty-eight cells on B. In the case of J the order of intensity was A, D, B, C, but 
the differences were not large and seemed to vary from time to time. The results of these experi¬ 
ments are given on Table III.


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