ON THE MAMMALIAN NERVOUS SYSTEM. 



359 



encephalon and the part observed interrupted the propagation of impulses from 

 the corresponding corona fibres. 



The hemisection was made in the case (Cat 225) before referred to, p. 356, two 

 months beforehand, at the 9th dorsal vertebra. For the observation the cord was 

 exposed, divided, and split longitudinally at the level of the 1st lumbar vertebra. 

 Both coronse radiatae were then exposed and excited alternately, the effects evoked 

 being given below. 



In this case it is evident that the effect was almost completely unilateral. 



In another case in which the hemisection was made at the time, there was no com 

 plete unilateral effect, but excitation of both coronse elicited changes, the corresponding 

 corona evoking an effect which was twice as large as that produced by stimulation of 

 the one on the opposite side to the lesion. By means of etherisation the proportion 

 was increased to 3 to 1, but since the alterations in excitability, due to the lesion 

 being performed at the time, were disturbing factors, the influence of which could not 

 be gauged, the experiment was not pursued further. It may be fairly concluded, 

 however, that the more perfect the elimination of such complications, the more 

 complete is the unilaterality of representation. 



V. Excitation of Corona Radiata after Complete, Removal of one Hemisphere. 



Effect in each Half of Divided Cord. 



In order to endeavour to ascertain whether the bilateral effect was in relation, not 

 merely with the discharge of portions of the cortex of the hemisphere opposite to that 

 of the excited corona, but also in relation with the basal ganglia and the cerebellum, 

 we have in one animal (Cat 309) observed the influence of complete removal of one 

 cerebral hemisphere. 



The cord was, in this case, split longitudinally, and both corona) exposed for 

 alternate excitation, the results of several observations being given below. 



