1911.] 



On Reflex Inhibition of the Knee Flexor. 



211 



which it often does, repetition of that same stimulus in the later course of the 

 background contraction will produce inhibitory decrement of the background 

 instead of excitatory increment (fig. 8, also fig. 6). In this case fatigue of the 

 background ipsilateral stimulation actually reverses the reflex effect exerted 

 by the contralateral afferent. 



iii. Rebound. 



With the flexor muscle and centre, as with the extensor, the with- 

 drawal of an inhibitory stimulus is frequently followed by a motor 

 discharge from the centre and in result a contraction of the muscle. In our 



Fig. 9. — Rebound contraction. Semitendinosus (cat, decerebrate). Lower signal marks 

 stimulation of ipsilateral afferent (combined peroneal-popliteal) ; upper signal marks 

 stimulation of contralateral afferent (combined peroneal-popliteal). On withdrawal 

 of the intercurrent inhibitory stimulus the reflex contraction caused by the ipsi- 

 lateral stimulus increases to beyond the grade it had prior to the inhibition. Time 

 marked above, in seconds. 

 VOL. LXXXIV. — B. e 



