1912.] Instability of Cortical Points. 255 



limited in appearance to relaxation alone — that is, to the replacement of 

 -contraction by inhibitory relaxation. 



Fig. 2. 



Experiment 14, Macacus sinicus, 21.2.12. — Record of a series of nine successive stimuli 

 of the same strength applied to an extensor-point. The first four of these evoke flexor 

 relaxation and extensor contraction, but the fifth gives a reaction of flexor contraction 

 and extensor relaxation, and this reversed reaction continues in the succeeding stimuli. 

 This shews reversal of an extension reaction to one of flexion during repetition of the 

 same stimulus applied to the same cortical point. It will be observed that at first there 

 is built up an extensor tonus, and that in the terminal part of the record a flexor tonus is 

 produced. It may further be seen that with the production of these states of tonus there 

 is a reciprocal diminution of the tonus of the antagonist. 



Amongst these reversals a case which should perhaps be considered apart 

 as belonging to a special category is that in which a flexion-point when 

 restimulated during the course of an epileptoid discharge started by its own 

 precedent stimulation produces, as it not infrequently does, prompt 

 inhibitory relaxation of the flexor muscle which it previously threw into 



