On the relative length 

 of the period of latency of the ocular muscles, 



when catted into action by electrical excitation of the motor and of 

 the sensory regions of the cerebral cortex. 



By 

 E. À. Schäfer, F. B. S., 



Jodrell Professor of Physiology in University College, London. 



(With two woodcuts.) 



The excitable portions of the cortex cerebri may be classed under 

 two heads viz: 1. Regions, electrical excitation of which produces cer-, 

 tain movements, and removal of which produces paralysis of the parts 

 previously moved, 2. Regions, electrical excitation of which produces 

 certain movements, and removal of which is unaccompanied by para- 

 lysis of such movements. Those parts which are grouped under the 

 first head form what is often termed the motor or psychomotor region *) 

 of the cortex, and comprise areas connected with movements of the 

 head and eyes, of the face and mouth, of the arm and leg, and of the 

 trunk. Of these the area which is connected with movements of the 

 head and eyes is, in monkeys, situated most anteriorly and when it is 

 excited electrically the head and eyes move to the opposite side, either 

 simply, or up or down, according to the point to which the electrodes 

 are applied. When, on the other hand, it is removed, the muscles moving 

 l he head and eyes to the opposite side, are paralysed. Similar movements 

 of the eyes (and sometimes also of the head) are produced by electrical 

 excitation of the superior temporal gyrus, middle temporal gyrus, angular 



Kinaesthetic region of Bastian. 



