The Excitable Cortex of the Chimpanzee, Orancj-Utan, and Gorilhi 218 



short-circuiting key. The stigniatic electrode in each animal was that 

 which was cathode at the break-induced current. The three electrodes 

 being applied, the primary current was then started by closing its key, and 

 the vibrating spring, about 40 per second, operated in the primary circuit. 





Fig. 29.— Scheme of faradisation for testing the relative excitability of the motor 

 cortex in cat, macaque monkey, and chimpanzee ; see text. 



The short-circuiting key in the secondary circuit was then opened. The 

 observation consisted in finding at what distance, as the secondary coil was 

 brought nearer to the primary, one or other animal gave a motor response, 

 and whether response was given by one or other animal under distinctly 

 weaker stimulation than by the other animals. 



Experiment, April 20. +, response (elbow flexion). 0, no responee. 



The results we obtained are illustrated by the above protocol. It will 

 be seen that there was no clear indication that response w^as elicited by 



