764 CORTICAL MOTOR REGION IK MAK. [BOOK in. 



the removal of a particular area leads, as an immediate result, 

 to the loss of the corresponding movement ; but while in some 

 instances recovery of the movement has in the monkey as in 

 the dog after a while taken place, in other instances the 4 paral- 

 ysis ' has appeared to be permanent. As a rule the paralysis 

 caused by a large lesion is not only more extensive, but also 

 of longer duration than that caused by a small one ; and natural 

 bilateral movements, as of the eyes, reappear earlier than uni- 

 lateral movements. The facts however within our knowledge 

 relating to the permanence of the effect are neither numerous 

 nor exact enough to justify at present a definite conclusion. 

 On the one hand the positive cases where recovery has taken 

 place are of more value than the negative ones, since in the 

 latter the recovery may have been hindered by concomitant 

 events of a nature which we may call accidental ; and it is at 

 least a priori most unlikely that the pyramidal tract mechanism, 

 if we may use the expression, though it may differ in the mon- 

 key and the dog in degree of development, differs so essentially 

 in kind that damage of it leads in the one case to permanent, 

 and in the other to mere temporary loss of function. We may 

 add that we should further expect to meet in the monkey with 

 more prominent and more lasting complications due to the sub- 

 sidiary effects of the operation, and it may be doubted whether 

 in any of the recorded experiments the animal has been allowed 

 to live a sufficient time for these subsidiary events to have 

 wholly cleared away, leaving only what we have called the 

 'deficiency' phenomena, due to the loss of the cortical area 

 alone. On the other hand it must be remembered that the 

 movements of the monkey are more intricate in origin, more 

 4 skilled ' than those of the dog ; it may be that differences in 

 the characters of movements determine the possibility of their 

 recovery ; and undoubtedly the coarser movements return first, 

 the finer, more skilled movements reappear later or not at all. 

 Thus, after the removal of an arm area in the monkey, a cer- 

 tain awkwardness in the movements of the thumb is one of the 

 lasting effects of the operation. 



488. So far we have spoken of changes in movements as 

 if these were the only effects produced by removal of the motor 

 area or of parts of it. But as a matter of fact changes in sen- 

 sations are as prominent results of such operations as changes 

 in movements, and this fact opens up a different view of the 

 matter. Before however we proceed any further in the discus- 

 sion, it will be of advantage to turn aside to what is known 

 concerning the cortical motor region in man. As we have 

 already said, theoretical considerations lead us to believe that 

 the cortical motor region in man is disposed in accordance with 

 the plan of the anthropoid ape as ascertained experimentally, 

 but with the differentiation carried still further; and observa- 



