1911.] 



On Reflex Inhibition of the Knee Flexor. 



213 



Fig. 10, a. — Sernitendinosus (cat, decerebrate). Increase of intensity of the reflex back- 

 ground on withdrawal of a weak intercurrent stimulus whose only obvious effect had 

 been pressor, not depressor. Lower signal marks stimulation of ipsilateral afferent ; 

 upper signal marks stimulation of contralateral afferent. Time marked above, in 

 seconds. 



Fig. 10, b. — Rebound after inhibitory stimulus which had, however, owing to toneless 

 state of muscle, produced no relaxation of the muscle. Semitendirwsus (cat, decere- 

 brate). Upper signal shows stimulation (faradic) of contralateral afferent (combined 

 peroneal-popliteal). The muscle at the time of application of this stimulus was 

 resting and without apparent tonus. No obvious effect beyond questionable slight 

 relaxations was caused by the stimulus during its application, but on its withdrawal 

 there ensued immediately an ample though short-lasting rebound contraction. Time 

 marked above, in seconds. 



4. Conclusion. 



Our observations show that the reflex influence of contralateral afferents 

 (hind-limb) on the knee flexor resembles that of the ipsilateral afferents on 

 the knee extensor.* In both cases moderate and strong stimulation produces 

 reflex inhibition, while weak stimulation under certain conditions produces 

 reflex contraction ; and with stimuli of intensity belonging to a somewhat 

 restricted range between weak and moderate the reflex effect is contraction 



* Sherrington and Sowton, 'Roy. Soc. Proc.,' B, 1911, vol. 83, p. 435. 



