Page:The American Journal of Psychology Volume 1.djvu/22

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LOMBAKD :

blow had been increased or decreased. These results will be better understood by reference to Fig. 1.

Fig. 1.

March 30th. 1887, 9.30 A. M.

3o° 30° 25^ 45° 50 c

The base line, o, shows the position of the recording needle when the leg is quiet, and each of the dots connected by the curve shows, in millimetres, the distance which the foot moved as a result of a blow on the ligamentum patellae. The experiments which are grouped together show how different may be the extent of the knee-jerks which are obtained by blows which have the same force and which are produced by letting the hammer fall through an arc of the number of degrees given at the top of the table. The heavy horizontal lines which cross such groups indicate the average of the enclosed experiments.

Search for errors in the method employed. — The fact that blows of the same force evoked knee- jerks of very variable extent was, as has been said, an entire surprise to us. The most careful examina- tion failed to reveal any mechanical cause. The hammer fell from exactly the same height and was released in just the same way each time, and as