1912.] 



Instability of Cortical Points. 



263 



Fig. 9. 



Experiment 9, Macacus rhesus, 9.2.12. E.F.E. — In this record a stimulus is twice 

 applied to an extension-point (C— D, I and II), and between the two applications a 

 flexion-point is stimulated (E — F). The first E stimulus gives a reaction of extensor 

 contraction followed by flexor-contraction, so that at the end of the period of stimulation 

 both the antagonists are in contraction at the same time. The F stimulus is then 

 applied, and a subsequent E stimulus then evokes a reaction consisting of contraction of 

 the flexor alone. This record demonstrated complete reversal of the extension reaction 

 by interpolated stimulation of a flexion-point. 



(b) Changes in the Response of a Flexion-Point following Excitation of an 

 Extension-Point. 



Just as repeated or strong excitation of a flexion-point often temporarily 

 diminishes or suppresses the subsequent response of an extension-point, 

 so conversely the response of a flexion-point is often temporarily lessened or 

 retarded or rendered more difficult immediately subsequent to similar stimu- 

 lation of an extension-point. The tendency of an E point thus to antagonise 

 an F point is, however, in our experience, distinctly less marked than is that 

 of an F point to suppress or to overcome an E point. Sometimes, however, 



