MOTOR AREAS OF THE HUMAN BRAIN 



641 



stimulation of the marginal convolution internally at the parts corresponding 

 with the ascending frontal and parietal convolutions, from the front back- 

 ward, produces movements of the arm, of the trunk, and of the leg. 



A good deal of doubt was thrown upon the experiments of Ferrier by 

 Goltz and other observers, from the results of excising the so-called motor 

 areas of the dog's brain. It was found that the part might be sliced away or 

 washed away with a stream of water, but that no permanent paralysis ensued. 



More extensive observations, however, have, in the main, confirmed 

 Ferrier' s original statement, at any rate with regard to the monkey's brain. 

 Destruction of the motor areas for the arm produces some permanent paraly- 

 sis 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 



ANUS A VAGINA 



OPENING 

 OF JAW 



VOCAL 

 CORDS 



MASTICATION 



FIG. 402. Scheme Showing the Motor Areas of the Brain. (Adapted from Griinbaum 

 and Sherrington by Cunningham.) 



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

 ever, 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 centers may be subserved 

 to a greater extent by the basal ganglia. 



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

 tance to discover how far the results 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 cor- 

 tical motor centers in the human brain, figure 402. 



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

 in the precentral convolutions and the walls of the adjacent sulci. 



