250 



Prof. C. S. Sherrington. Break-shock 



reflex. They and the course of the contraction suggest that in the 

 decerebrate preparation the contraction of this ipsilateral reflex is possibly, 

 in some cases, the rebound phase of a diphasic reaction, wliose first phase is 

 mainly inhibitory, owing to admixture of concurrent inhibition and contrac- 

 tion, although the inhibition cannot, owing to absence of actual contraction in 

 the muscle at the time when the reflex is initiated, make itself apparent by 



popr. 



16 cm 









12-5 cm. 

 30 cm. 













msscm. 



m.iscm 









Fig. 5. — Similar to fig. 1, but from a decerebrate preparation instead of a spinal pre- 

 paration. The upper two insets are reflex contractions (tibialis anticus) evoked by 

 single break-shock to central stump of popliteal nerve ; the numerals against each 

 inset indicate the coil distances — the shocks for the reflex contractions are very 

 strong ; in the middle inset the break-shock at coil distance of 30 cm. produced no 

 contraction. The lower two insets are maximal twitches evoked by break-shock to 

 motor nerve at 16 cm. and 35 cm. respectively. Time ordinates and tension abscissae 

 as in fig. 1. Stimulus-signal below. 



any relaxation of the muscle, but only by delay and reduction of the ensuing 

 contraction. 



The observations, in so far as they cover the ground of those reported in the 

 two previous papers (1 and 2) confirm and amplify them. (1) A single break- 

 shock of moderate intensity, applied to a bared afferent nerve, not rarely 

 evokes a reflex contraction exceeding in tension and duration the " maximal " 

 twitch elicitable by break-shock stimulation of the motor nerve itself. 

 (2) The rise of tension in the reflex contraction very soon after its first onset 

 is not rarely of steeper gradient than is that of maximal twitch. This 

 steeper gradient is observable in some instances even before the termination 

 of the first 0-01" from commencement of the contraction. (3) The maximal 



