There are large mean variations in Table XI., as would be anticipated.  Since the reactions were taken in sets of 24, the means of each set as well as that of the total are given, and also, in columns 4 and 5, the means of the first half and the last half of each set.

A comparison of Tables XI., XII. and XIII. makes clear the differences in reaction time correlated with differences in the strength of an electric stimulus.  For Table XI., series I, the relative value of the stimulus was I; for Table XII., series 2, it was 2, and for Table XIII., series 3, it was 4.  Throughout the series from I to 3 there is a rapid decrease in the reaction time and in the variability of the same.  The reaction time for stimulus I, the so-called threshold, is given as 300.9[sigma]; but of the three it is probably the least valuable, for reasons already mentioned.  The mean of the second series, stimulus 2, is 231.5[sigma] while that of the third, stimulus 4, is only 103.1[sigma].  This great reduction in reaction time for the four-cell stimulus apparently shows the gradual transition from the deliberate motor reaction, which occurs only after complex and varied central neural activities, and the purely reflex reaction, which takes place as soon as the efferent impulse can cause changes in the spinal centers and be transmitted as an afferent impulse to the muscular system.

TABLE XI.

ELECTRICAL STIMULUS REACTION TIME.  SERIES 1.

Average             Average of   Average   Average   Mean Var
Frog.   of all.   Mean Var.     Sets.     of 1st h.  of 2d h.  of Sets.

1     238.5*     33.3*     216.0*      205.6*     226.7*    33.2*
261.0       248.0      274.1     33.3
2     458.0     219.0      458.0       270.4      643.8    219.0
4     273.4      59.9      273.4       245.7      301.1     59.9
5     263.9      50.5      268.6       244.7      292.5     44.9
259.2       236.0      282.4     56.1
6     271.1      65.1      322.6       273.2      372.0     87.9
219.6       208.5      230.6     42.3
Gen Av. 300.9      85.5      300.9       244.8      356.8     85.5

Totals. 
For No. 1 the averages are for 2 sets of 24 reactions each,    48
"   2     "          "    one set of 12      "     "       12
"   4     "          "    one set of 24      "     "       24
"   5     "          "    two sets of 24     "     "       48
"   6     "          "    two sets of 24 and 12 reactions,
respectively,                36

Transcriber’s Note:  All values in [sigma], 1/1000ths of a second.

TABLE XII.

ELECTRICAL STIMULUS REACTION TIME.  SERIES 2.