1912.] 



Instability of Cortical Points. 



261 



the responses a few times at given intervals, the effect of interpolating a 

 stimulation of a flexor-point in such an interval can be examined. The 

 result of this interpolation is not infrequently practically to suppress the 

 response of the E point for the time being, or to reduce one or other or both 

 of its components (contraction and relaxation) very markedly (figs. 7, 8). 



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f ~c7J~j> i i F c 73 b 







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Fig. 7. 



Experiment 8, Mocacus rhesus, 29.1.12. E.F.E. — Record of two reactions evoked on 

 stimulation of the same extension point (C — D, I and TI) with an interpolated stimulation 

 of a flexion-point (E — F). The first stimulation of the extension-point gives a marked 

 extensor contraction and flexor relaxation. On its cessation there is a state of extensor 

 tonus. This is broken down on stimulation of the flexion-point, and there is a marked 

 flexor contraction, which persists after the cessation of the stimulus. The second applica- 

 tion of the extension-point stimulation gives a certain degree of flexor relaxation (but not 

 to such an extent as before) and no extensor contraction. This shows an approximation 

 to reversal — that is to say, depression of both factors in the extension response. 



Sometimes, however, the effect is an actual reversal of the usual response 

 of the E point. The reversal may be partial or complete. In the former 

 case the extinction of the contraction of the extensor may predominate. In 



