SINCE 1875 when Erb1 and Westphal2 critically described the movement of the limbs elicited as muscle stretch reflexes, many methods of recording and clinical observations of the knee-jerk have been reported. The exaggerated knee-jerk has been recognized as one of the most striking and fundamental aspects of spasticity. According to the accumulated literature, the typical patterns of knee-jerk in the hemiplegic limb as compared with the normal limb of the same patient are as follows: (1) The lower threshold of excitation; the lower intensity of stimulation necessary to produce the first perceptible response (Prichard3); (2) At the same force of stimulus, both the mechanical response of the leg and the electrical response of the quadriceps muscle are of greater amplitude and are very constant (Prichard,3 Miglietta and Lowenthal4); (3) The mechanical response has a closer resemblance to the perpendicular curve of ascent, invariably a well-marked