On the relative length of the period of latency of the ocular muscles etc > 15fj 



Having ascertained that movement of the eyes toward the left was 

 easily obtainable by excitation on the right side of the brain of all 

 the posterior excitable region (superior temporal, posterior limb of 

 angular, occipital) as well as by excitation of the frontal area for that 

 movement, I cut away the latter area upon the right side as comple- 

 tely as possible, including, so as to be quite sure of the entire removal 

 of the area in question, almost the whole of the frontal lobe in ad- 

 vance of the fissure of Rolando. The removal produced a permanent 

 direction of the eyes, (and head) to the right. But on now exciting 

 the posterior regions of the right hemisphere the eyes were still moved 

 towards the opposite side. I now cut through the corpus callosum and 

 again excited the posterior regions of the right hemisphere with the 

 same result. 



Next I proceeded to cut away the whole of the left frontal lobe 

 in advance of the fissure of Rolando. Excitation of the superior tem- 

 poral gyrus or occipital lobe of either side still produced movements 

 of the eyes towards the side opposite to that stimulated. It is clear 

 then that these posterior excitable regions do not necessarily produce 

 the movement in question by calling into activity the grey matter 

 of the frontal cortex, and the centre through which they operate, after 

 removal of that grey matter, must be looked for in some more deeply 

 seated portion of the brain (very probably in the grey matter of the 

 corpora quadrigemina). At the same time this is no evidence that 

 when the frontal cortex is intact they do not operate through that centre. 

 It might seem that this point could be determined by taking the la- 

 tency of excitation of the posterior regions after removal of the an- 

 terior and comparing this latency with that obtained before the removal. 

 But such comparison would have no value since the condition of the 

 tissue would certainly be very different, owing to the haemorrhage and 

 shock of the removal, as well as from the impossibility of knowing 

 whether the state of anaesthesia were the same. 



