152 



E. A. Schäfer, 



given in fig. I. In many cases the (metallic) point of the muscle-lever 

 was not allowed to scratch the paper, since this might have introduced 

 another error from the varying friction against the blackened surface, 

 but was kept just away from the surface, so that the muscle curves 

 described were traced by the passage of the electric sparks alone. 



Fig. 1. Diagram showing the method employed for determining the relative la- 

 tency of the motor and sensory regions of the cortex cerebri. 



L, light metallic bell-crank lever transmitting the sparks from a Ruhmkorff coil, 

 B, to a cylinder, Cy, revolving by clockwork. T, silk thread attaching the lever to 

 one of the eyes. G, Grove battery, working the interruptor of the Ruhmkorff. H, Helm- 

 holtz key by means of which the short-circuiting circuit, S.C, of the DuBois-Rey- 

 mond coil, D. B, is opened and the induced interrupted current is sent from that coil 

 through the switch, Siv, to either of the electrodes the same instant that the circuit 

 of the Ruhmkorff is made. D, Danieli battery working the Du Bois-Reymond coil. 

 M, wires passing to electrodes placed on the motor region of the hemisphere. S, wires 

 passing to electrodes placed on one of the sensory regions. 



Fig. 2. Tracings showing the relative latency of the ocular muscles on alter- 

 nate excitation of the frontal and occipital regions of the hemisphere. 



The results obtained are strongly in favour of the view that the 

 mechanism of the anterior (psychomotor) centre is more direct in its 



