FUNCTIONS OF THE BRAIN 957 



general are, although perhaps weakened, never completely para- 

 lyzed. This is an indication that each member of such functional 

 pairs of muscles is innervated from both hemispheres; and this 

 physiological deduction is supported by the anatomical fact already 

 referred to, that after removal of the ' motor ' cortex, or injury to 

 the pyramidal tracts in the internal capsule or crus, some degener- 

 ated fibres (homolatexal fibres) are found in the crossed pyramidal 

 tract on the side of the lesion (p. 875)- 



In the dog after a time the paralysis may more or less completely 

 disappear. In the monkey restoration is less complete. 



Some interesting observations have been made 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 en- 

 tirely 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 diminution in the sensibility of the skin of these limbs. 

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

 of 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 movements 

 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 

 normal 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. 



In the lower monkeys the ' motor ' area was formerly stated to 

 extend behind the sulcus centralis into what in man would be called 

 the ascending parietal convolution (post-central gyrus), and also to 

 be more extensively represented on the mesial surface of the hemi- 

 sphere than in the higher apes. Such observations, however, require 

 to be reinterpreted in view of the results of Sherrington and Griin- 

 baum, especially as they were carried out by the bipolar method of 

 stimulation, with both electrodes on the cortex. This method does 

 not admit of such strict localization of the stimulus as the unipolar 

 method. The most recent work with the unipolar method has 



