702 REMOVAL OF CORTICAL AREAS. [Book hi. 



§ 487. These skilled movements are to a large extent, 

 though not exclusively, voluntary movements. We have in a 

 previous section seen reason to believe that the cerebral cortex 

 is in some way especially associated with the development of 

 voluntary movements. Putting together this conclusion and 

 the conclusions just arrived at we are naturally led to the 

 further conclusion that the cortical motor region, with the 

 pyramidal tract belonging to it, plays an important part in carry- 

 ing out voluntary movements. Do other facts support this 

 view, and if so, what light do they throw on the question as 

 to what part and what kind of part the motor region thus 

 plays ? 



In this connection we naturally desire to know what are the 

 results of removing from an otherwise intact animal the whole 

 motor region, and more especially this or that particular por- 

 tion of it. Before proceeding further, however, we may once 

 more call attention to the caution given in § 457, and repeated 

 in § 476 ; indeed when we consider the high organization and 

 complex functions which obviously belong to the cortex, when 

 we bear in mind that it appears to govern, and must therefore 

 be bound by close ties to almost all the rest of the central ner- 

 vous system, we must be prepared to find after removing a por- 

 tion of cortex that the pure ' deficiency ' phenomena, those 

 which result from the mere absence of a piece of the cortex, 

 are largely obscured by the other effects of the operation. 



In the rabbit the results have been almost purely negative. 

 When in this animal the part of the cortex which may be con- 

 sidered as the motor region is removed, nothing remarkable is 

 observed in the movements of the animal. We can hardly sup- 

 pose that the operations of the central nervous system are the 

 same in an operated as in an intact animal, and the differences 

 induced ought to be betrayed by the movements of the body ; 

 but at present they have escaped observation. 



In the dog the removal of an area is followed by a loss or 

 diminution of voluntary movement in the corresponding part of 

 the body. When, for instance, the area for the fore limb is 

 removed from the left hemisphere, the right fore limb is com- 

 pletely or partially ' paralyzed.' In carrying out its ordinary 

 movements the operated animal makes little or no use of its 

 right fore limb. Bnt this state of tilings is temporary only. 

 After a while the animal regains power over the limb, and in 

 successful cases recovery is so complete that it is impossible to 

 point out in the limb any appreciable deviation from the nor- 

 mal use. And careful examination after death has shewn not 

 only that the area had been wholly removed, but also that there 

 was no regeneration of the lost parts ; the removal of the cor- 

 tex leads in such cases, as usual, to defeneration of the corre- 

 sponding strand in the pyramidal tract right away from the 



