194 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



complex without anatomical lesion. It must also be borne in mind 

 in this connection that most of the efforts made hitherto to localize 

 the functional activities of the brain have had reference chiefly to 

 planes of separation vertical to the cortex. As indicated on p. 185, 



Fig. 86.— To show the motor areas in the dog's brain as originallj' determined by Fritsch 

 and Hitzig: s, Sigmoid gyrus; A, center for the neck muscles; +, center for the extensors and 

 adductors of the foreiimb; +, center for the flexors and rotation of forelimb; if, center for the 

 hind limb:, Q — 0< center for the muscles innervated by the facial. 



recent investigations have indicated that it will be necessary to 

 consider also the separation of function along horizontal planes 

 (von Valkenburg) . That is to say, it seems quite possible that the 

 several strata in the cortex, such as the granular, the infra- 

 granular, and the supragranular layers may mediate different ac- 

 tivities of the brain, or even different psychical functions. 



The Motor Area. — The first experiments of Fritsch and Hitzig 

 disclosed the location of a cortical region in the dog which upon 

 stimulation gave definite movements. The later experiments of 

 Ferrier, Schafer, Horsley, and Beevor, particularly upon the apes, 

 gave reason for believing that this motor area surrounds the 

 central sulcus of Rolando and extends inward upon the mesial 

 surface of the cerebrum. Its exact boundaries marked out by 



