THE CEREBRO-SPINAL NERVOUS SYSTEM. 



519 



nent paralysis ensued. Burden-Sanderson, too, showed that stimulation 

 of different points in a horizontal section, through the deeper parts of 

 the hemispheres, produces the same effects as stimulation of the so-called 

 ' centres." 



More extensive observations, however, have confirmed Ferrier's origi- 

 nal statement, at any rate with regard to the monkey's brain. Destruc- 

 tion of the motor areas for the arm produces permanent paralysis of the 

 arm of the opposite side, and similarly of that for the leg, paralysis of 

 the opposite leg. If both areas are destroyed permanent hemiplegia 

 ensues. Paralysis of so extensive and permanent character does not, 

 however, appear the rule when the brain of a dog is used instead of that 

 of the monkey. It is suggested that in the animal lower in the scale, 

 the functions which in the monkey are discharged by the cortical centres 

 may be subserved by the basal ganglia. 



Motor ial Areas of the Human Brain. It is naturally of great im- 



FIG. 358. Motorial areas of the brain. A.F., ascending frontal convolution; A P., ascending 

 parietal; F.R., fissure of Rolando; F. Sy., sylvian fissure. (After Gowers.) 



portance to discover how far the result of experiments upon the dog and 

 monkey hold good with regard to the human brain. Evidence furnished 

 by diseased conditions is not wanting to support the general idea of the 

 existence of cortical motorial centres in the human brain (Fig. 358). 



So far, however, it has been possible to localize motor functions in 

 the frontal and ascending parietal convolutions, only to the convolu- 

 tions which bound the fissure of Rolando, and to those on the inner side 

 of the hemispheres which correspond thereto. 



The position of the centres is probably much the same as in the 

 monkey's brain those for the leg above, those for the arm, face, lips, 

 and tongue from above downwards. Destruction of these parts causes 

 paralysis, corresponding to the district affected, and irritation causes 

 convulsions of the muscles of the same part. Again, a number of cases 

 are on record in which aphasia, or the loss of power of expressing ideas 



