350 MESSRS. F. GOTCH AND V. HORSLEY 



gauged beforehand, so that the latter is not thrown into a hyperexcitable state, then 

 the above mentioned phenomenon can invariably be obtained, and this not only in 

 the Monkey but also in the Cat. It might be objected that the cortex was not 

 completely discharged, but we regard the overflow of the excitatory changes into the 

 neighbouring foci as sufficient evidence of the required completeness. Moreover, the 

 converse position, viz., the appearance of bilaterality tells the same (story see pp. 

 354 and 359), and thus forms the crucial argument. 



If we are warranted, therefore, in our view that the cortex under these circumstances 

 is completely discharged, the above described phenomenon negatives the practical 

 existence of bilateral representation of the limb muscles in these animals. 



(3.) When (" bilateral"} movements of both limbs follow excitation of one hemi- 

 sphere after the excitable cortex of the opposite hemisphere has been thrown out of gear 

 by ablation, division of the commissures, &c., &c., the movement of the limb on the side 

 opposite to the cortex excited is the complete cortical effect of tonic folloived by clonic 

 contractions, whereas the movement of the limb on the same side as that of the cortex 

 excited is only a tonic contraction. 



If bilateral movements of both limbs receive their originating impulses directly 

 from one cortex, it is not comprehensible why the above-mentioned striking difference 

 in the kind of movement of the limbs should exist. This difference, specially insisted 

 on by one of us,* has been also observed by several authors (LEWASCHEW, &c.), and 

 it suggests that the movement noted on the same side as the excitation is of some 

 origin other than the cortex (its corresponding cortical apparatus being destroyed, be 

 it remembered), for a simple tonus lasting during the excitation is characteristic not 

 only of the cortex but of the cerebellar or other lower centres. 



(4.) When bilateral movements of limbs are observed, those of the limb of the same 

 side as the cortex excited are always later in commencement than those of the opposite 

 side. (FBANCK and PITKES.) 



This delay in movement of the limb of the same side is attributed by most to loss 

 of time in traversing basal commissures. There is no means of testing this view 

 except by some arrangement in which the exclusion of the said commissures is 

 provided. As far as the commissures in the cord are concerned, this might be achieved 

 by ascertaining the time relations of such excitatory electrical changes as will pre- 

 sently be shown to appear in each half of the longitudinally divided cord upon 

 stimulation, of the cortex. 



(5.) All experiments on this subject have included in their anatomical plan the 

 cerebellum, ivithout excluding its functional influence. 



In our own experiments about to be described, as well as those of the authors 

 already quoted, the cerebellum has been left in normal connection with the central 

 structures excited. 



In performing the experiment of exciting one hemisphere after ablation of the 



* V. H., loc. cit. 



