Page:The American Journal of Psychology Volume 1.djvu/12

 6 LOMBARD :

to a still greater degree, all influences which vary the activity of the central nervous system as a whole, or of special mechanisms of the spinal cord and brain.

Of the many names which have been given to this phenomenon, viz.: "knee phenomenon," "patellar tendon reflex," "myotatic contraction," "knee-kick," "knee-jerk," the last has commended itself to the writer, because it calls attention to the peculiar sud- denness of the movement, and does not imply any- thing with regard to the nature of the process.

The author takes this opportunity to express his thanks to Prof. H. Newell Martin and Professor G. Stanley Hall, for their valuable advice and their great courtesy. He takes pleasure, also, in acknowl- edging his indebtedness to his co-worker in this research. All the experiments were made upon the writer by his wife, and their value is greatly enhanced by the accuracy and care with which her work was done.

Method of Producing the Knee-Jerk, and the Nature of the Process. — Place the subject in an easy position, with his knee partly flexed, and his leg freely movable ; then strike the middle of the ligament, just below the knee pan, a sudden blow. The kick which results has a jerky character, which is quite peculiar.

If a man sits with one leg crossed over the other, the quadriceps muscle of the leg that is uppermost is slightly stretched by the weight of the suspended leg and foot, and the chain composed of the quadriceps tendon, the patella and the patellar ligament, which connects the quadriceps