630 CEREBRAL CONVOLUTIONS. [BOOK in. 



to the area. We may very fairly imagine that when a dog wills to 

 extend the forelimb, the cerebral changes are of such a kind that 

 eventually processes are set up in the grey matter of the area for 

 extension of the forelimb similar to those which arise from stimu- 

 lation of the area. But if this be the case, then removal of the 

 area ought permanently to remove also, from the dominion of the 

 will, the muscles employed in extension of the limb; the chain of 

 events leading down from the inception of the voluntary effort to 

 the actual contraction of the appropriate muscles ought to be 

 broken in the link constituted by the events occurring in the 

 cortical area; the dog ought thereafter to be unable to extend his 

 forelimb by any direct effort of the will. The results of experiment 

 however shew that this is not the case. Immediately after the 

 operation by which the area is removed, more or less paralysis it is 

 true may be observed in the corresponding muscles. But this soon 

 passes away, and complete power over the muscles may be re- 

 gained. The temporary paralysis seems to be a sort of inhibitory 

 effect due to the injury caused by the operation; and, though the 

 experiment confirms the view that some special connection exists 

 between the cortical area and the appropriate group of muscles, it 

 disproves the view that the area serves as a direct instrument 

 of the will. Nor can we take refuge in the idea that some other 

 area has taken up vicariously the duties of the lost area. This is 

 disproved by the observations of many inquirers which go to shew 

 that not only many different parts of the brain, but a very large 

 portion of the whole brain, may be removed without any clear and 

 definite paralysis of any group of muscles being occasioned. In the 

 experiments of Goltz, which we shall mention directly, the loss of a 

 large mass of the cerebral convolutions diminishes the movements 

 of the body inasmuch as it curtails the general action of the 

 intelligent will which brings them about, but does not withdraw 

 any particular sets of muscles from the influence of the so to speak 

 shortened will which is left to the animal. Indeed we have reason 

 to think that when in such operations directed solely to the 

 removal of the cerebral convolutions, paralysis of any particular 

 group of muscles occurs, mischief must unwittingly have been done 

 to other parts of the brain. 



What then can we conclude as to the nature of the events 

 which take place in the several .cortical areas ? To this question 

 unfortunately no clear answer can yet be given; for the results 

 of different inquirers are so far irreconcilably opposed. 



On the one hand, one observer (Munk) states that the re- 

 moval of a certain area in the posterior lobes produces no other 

 effect whatever but blindness. He further states that removal 

 of small portions of the area leads to partial blindness, that is 

 to the formation so to speak of artificial blind spots in the field of 

 vision corresponding to the spots of cerebral cortex removed; so 

 that the retinal image may be conceived of as projected as it were 



