Page:The American Journal of Psychology Volume 1.djvu/65

 NORMAL KNEE-JERK. 59

30, 39, 53, 37, 29. The increase and decline of the knee-jerk as the music approached and died away, and the difference in the effect of the bands, the drum corps and the street sounds, is very interesting. The fact that the character of the music determined its power to reenforce the knee-jerk was still more clearly illustrated in an experiment made on April 6. The average knee-jerk at 8 P. M. was 32 mm. and the average knee-jerk at 11 P. M. was 29 mm. It is fair to assume that at 10.30 P. M., the time of the experiment, the average knee-jerk during quiet would not have been far from 30 mm. The music used in this experiment was a good piano in a neighboring room, played by a skillful pianist. While Beethoven's "Funeral March" was being played the knee-jerks were, viz.: 82, 104, 96, 105, 104,-99, 108, 95, 106, 118, 117, 90, 113, 119, 97, 100, 124, 108, 112, and the aver- age was 105. This was followed by an interval of quiet, during which the knee-jerks fell off — 83, 90, 90, (56, 82, 59, 75, 50; average, 74. Then Chopin's "Raindrop Prelude" was played, and to our delight, when we came to read the results we found that the extent of the knee-jerk had varied with the character of the music in the most remarkable manner. Thus, during the soft music, when the raindrops are sup- posed to be falling, the knee-jerk was 52, 63, 47, 50, 55 ; as the music changed and the deeper passages began to make themselves felt, it was 66, 73, 58, 78, 70, 86, 77, 87 ; as the music subsided and became softer the measurements were 66, 43, 59, 62, 71, 68, 54 ; as the more thrilling passages succeeded 79, 86, 86 was measured, and finally, as the varied but softer parts came again, the knee-jerk was 58, 57, 79, 67, 47. As has been said, the average of the knee-jerk during