Page:The American Journal of Psychology Volume 1.djvu/26

 20 LOMBARD :

released by a slight movement of the lever, and, inas- much as it always fell from the same height, it always struck a blow of the same force. The blows were given at intervals of fifteen seconds, and they struck the same part of the ligament each time. For the sake of accuracy all the experiments were made on the bare leg, although examination showed that nearly the same results could be obtained when the knee was covered by a thin layer of clothing. Throughout all the experiments the subject lay with closed eyes, in an absolutely comfortable position, and, as far as was possible, not only avoided all vol- untary movements, but directed his thoughts away from the experiment and to some indifferent subject. During the earlier experiments the blows of the ham- mer were each distinctly felt, but later they were often scarcely noticed, and in many cases the subject went, before the end of the examination, almost, if not quite, asleep.

The following tables give, as far as possible, an accurate account of the experiments and of the con- dition of the subject at the time that each examina- tion was made. The extent of the movement of the foot resulting from each knee-jerk was accurately measured in millimeters, and tabulated ; inasmuch, however, as the reader can be given no correct idea of the subtler influences which governed the extent of each separate knee-jerk, it does not seem profit- able to report all these measurements, and only the average of the experiments made at each examina- tion is given. In most cases, indeed, the more deli- cate influences which determined the extent of the knee-jerk remained undiscovered, but, at times, they unexpectedly revealed themselves, and these discov-