Group 1 of the electrical reactions were taken under the following conditions.  A reaction box about 40 cm. in diameter was used.  The mean temperature of the experimenting room was about 20 deg.  C. In all cases the string was attached to the left hind leg of the frog, and the stimulus applied to the middle of the gastrocnemius muscle of the right hind leg.  Reaction times were taken in series of ten, excluding those which were imperfect.  As the moistness of the skin affects the strength of the electric stimulus received, it was necessary to moisten the animal occasionally, but as it did not seem advisable to disturb it after each experiment this was done at intervals of five minutes throughout the series.  Were it not for this precaution it might be said that lengthening of the reaction times toward the end of a series simply indicated the weakening of the stimulus which resulted from the gradual drying of the skin.  The stimulus in this group was applied by means of the stimulating apparatus of Fig. 6.  It is merely two wire electrodes which could be placed upon the animal, with the additional device of a key for the breaking of the chronoscope circuit the instant the stimulus was given.  The most serious objection to this method of stimulating is that there is a tactual as well as an electrical stimulus.

Before presenting averages, two representative series of reactions may be considered.

SERIES I. FROG B. APRIL 9, 1900. 10 A.M.

  Temperature 19 deg.  C. String to left hind leg.  Stimulus to right hind
  leg.

  Strength of stimulating current 1.0 volt, .0001 ampere.

  Number of
  Experiment.  Hour.  Reaction Time.  Remarks.

1        10.25                   No reaction.
2        10.27                   No reaction.
3        10.30        139[sigma]
4        10.34        164
5        10.35        102
6        10.37        169
7        10.39        151
8        10.40        152
9        10.42        144
10        10.43        152
11        10.45        122
12        10.51        179
13        10.54                   No reaction.

Average of 10, 147.4[sigma]

SERIES 2.  FROG F. ELECTRICAL STIMULUS.

No.  Hour.  Reaction Time.  Remarks.  Deviation from Mean.

1 10.19 35[sigma] Probable reaction
to visual stim.
2 10.22 173 4.7
3 10.24 161 — 7.3
4 10.25 133 -35.3
5 10.26 199 30.7
6 10.28 130 -38.3
7 10.32 179 10.7
8 10.34 187 18.7
9 10.35 60 Probable reflex.
10 10.37 183 14.7
11 10.38 166 — 2.3
12 10.39 172 3.7