1911.] 



On Reflex Inhibition of the Knee Flexor. 



207 



inhibitory influence of the contralateral afferent is particularly easily and 

 strikingly obtainable when pitted against the after-discharge contraction 

 which frequently follows and prolongs, for a short time, a strong reflex after 

 the strong stimulus which excited the contraction has been itself withdrawn. 

 So also the inhibitory effect is markedly well obtained against the contraction 

 elicited by a mechanical stimulus applied to the pinna of the ear. Occasion- 

 ally in the decerebrate preparation the semitendinosus enters into somewhat 

 prolonged reflex contractions whose source is not clear (fig. 6) ; and against 



Fig. 5.— Similar intercurrent stimuli opposed to reflex backgrounds given by faradic and 

 galvanic stimuli respectively. Lower signal marks stimulation of ipsilateral afferent by 

 weak faradisation (30 Kronecker units) in a and b, by galvanic currents delivered by 

 v. Kries rheonome in c and d. Upper signal marks weak stimulation (faradic) of contra- 

 lateral afferent, secondary coil at 18 cm. for a and c, at 24 cm. for b and d. The inhibitory 

 effect is more marked against the galvanic background. Time above, in seconds. Semi- 

 tendinosus (cat, decerebrate). 



these also the inhibitory effect of the contralateral afferent is extremely 

 easily exerted. 



And there is a further factor attaching to the background stimulation 

 which likewise influences the effect of the contralateral afferent. When a 

 given contralateral stimulus is repeated at intervals during the course of a 

 prolonged reflex contraction, its inhibitory effect is greater in the later 

 repetitions than in the earlier. This increase is regularly progressive and is 

 often very marked (fig. 7, also fig. 6). It shows itself particularly when the reflex 



