THE CENTRAL NERVOUS SYSTEM 747 



cortex, or injury to the pyramidal tracts in the internal 

 capsule or crus, some degenerated fibres (homolateral fibres) 

 are found in the crossed pyramidal tract on the side of the 

 lesion (p. 688). 



Removal of a single motor region leads to paralysis only 

 of the corresponding limb, or part of a limb, on the opposite 

 side. In the dog after a time the paralysis may more or 

 less completely disappear, the loss of the cortical centres on 

 one side being perhaps compensated by increased activity 

 of those that are left. In the monkey restoration is less 

 complete ; in man it is more imperfect still. 



Goltz has lately reported some interesting observations on a monkey, 

 which was carefully watched for eleven years after the removal by 

 two operations of the cortex of the greater portion of the frontal and 

 parietal lobes on the left side. The character of the animal, which had 

 been studied for months before the operations, was entirely unaffected, 

 All its traits remained unaltered. There was no loss of memory or 

 intelligence. On the other hand, disturbances of movement on the 

 right side were very noticeable up till its death. It learned again to 

 use the right limbs in locomotion; but, although they were not 

 markedly weaker than those of the left side, their movements had a 

 certain clumsiness, which was associated with a permanent diminu- 

 tion in the sensibility of the skin of these limbs. Muscular 

 sensibility was also lessened. In acts requiring the use of only 

 one hand, the right was never willingly employed, and it evidently 

 cost the animal a great effort to use it in such movements, but 

 by special training it learnt again to give the right hand when 

 asked for it, and to make use of it for other purposes. The move- 

 ments with which the motor areas are concerned are essentially 

 skilled movements, and we may suppose that it is more difficult for 

 a monkey to educate again a centre for such complex and elaborate 

 manoeuvres as are performed by its hand than for a dog to regain 

 cortical control of the comparatively simple movements of its paw. 

 In man in cases of hemiplegia, when the patient lives for some time 

 a certain amount of recovery usually takes place, especially in young 

 persons, in the paralyzed leg, but much less in the paralyzed arm. 



It is in the light of the results obtained in monkeys, and by the 

 aid of clinical and pathological observations, that the motor areas in 

 man have to a great extent been mapped out. An extensive 

 haemorrhage involving the cerebral cortex on both sides of the fissure 

 of Rolando, or an embolus blocking the middle cerebral artery, 

 causes paralysis of the opposite side of the body. An embolus of 

 a branch of the middle cerebral artery causes paralysis of the muscles, 

 or rather movements, represented in the area supplied by it. A 

 tumour causes symptoms of irritation, motor or sensory convulsions 

 beginning in, or sensations referred to, the parts represented in the 

 regions on which it presses. ID connection with the localization 



