THE MOTOR FUNCTION OF THE CEREBRAL CORTEX 639 



dog were entirely absent in the child. The child kept up a perpetual crying 

 from the second year on, but the crying could be stilled by pressure, especially 

 about the head. The child had no control over its functions and showed no 

 consciousness of physical discomfort. "This child without cerebrum was 

 even less active than a decerebrate fish or frog." 



In comparing the reactions of this child with those of the decerebrate dog, 

 it must be remembered that the operated dog has not only a more mature cord 

 and medulla, but also an intact and well developed thalamus. The nuclei 

 of the thalamus may quite possibly carry on extensive nerve co-ordinations 

 which were of course lacking to the child. However, the child possessed the 

 necessary basic nervous mechanism for the control of respiration, circulation, 

 digestion, alimentary motion, etc., adequate for the purely physical life. 

 The case is only another link in the chain of evidence which more firmly 

 establishes the view that the entire psychic life is inseparably associated with ' 

 the normal physiological functioning of the cerebral cortex. 



LOCALIZATION OF THE MOTOR FUNCTION OF THE CEREBRAL 



CORTEX. 



The experiments upon the brains of various animals by means of electrical 

 stimulation have demonstrated that there are definite regions of the cerebral 

 cortex the stimulation of which produces definite movements of co-ordinated 

 groups of muscles of the opposite side of the body. Fritsch and Hitzig were 

 the first to show that the cerebral cortex responds to electrical irritation. 

 They employed a weak constant current in their experiments, applying a 

 pair of fine electrodes not more than one- twelfth inch apart to different parts 

 of the cerebral cortex. The results thus obtained have been confirmed and 

 extended by Ferrier, Sherrington, and many others, stimulating chiefly with 

 induction currents. 



The fundamental phenomena observed in all these cases may be thus 

 epitomized: 



i. Excitation of the same spot on the cortex is always followed by the 

 same movement in the same animal. 2. The area of excitability for any 

 given movement is extremely small, and admits of very accurate definition. 

 3. In different animals excitations of anatomically corresponding spots pro- 

 duce contractions in similar or corresponding muscles. 



The various definite movements resulting from the electric stimulation 

 of circumscribed areas of the cerebral cortex are enumerated in the descrip- 

 tion of the accompanying figures of the dog's and monkey's brains. 



In the case of the dog the results obtained are summed up as follows by 

 Hitzig: i. One portion, anterior, of the convexity of the cerebrum is motor; 

 another portion, posterior, is non-motor. 2. Electric stimulation of the 

 motor portion produces co-ordinated muscular contraction on the opposite 

 side of the body. 3. With very weak currents, the contractions produced 



