LOCALIZATION OF THE CEREBRAL FUNCTIONS. 647 



the angular gyri and all the posterior lobes be destroyed, the ani- 

 mal remains blind. 



5. Extensive areas of the brain surface may be stimulated me- 

 chanically, chemically, or electrically, without the least response 

 being shown by the animal, to indicate either sensory or motor 

 excitations. 



6. Stimulation of the convolutions around the fissure of Rolan- 

 do, however, gives rise to definite coordinated movements of mus- 

 cles of the other side of the body. Indeed, local groups of muscles 

 respond with surprising constancy to the electric stimulation of 

 certain definite parts of the cortex. These convolutions have thus 

 been mapped out into motor centres for hind limb, fore limb, face, 

 etc. 



From this we are tempted to conclude (1) that the cortex of 

 the posterior region of the hemispheres is related to the reception 

 of some sensory impressions ; (2) that the superior and lateral 

 part in the neighborhood of the fissure of Rolando is related to 

 the discharge of voluntary motor impulses ; and (3) that the an- 

 terior lobes are not immediately subservient to either the sensory 

 or motor functions of the hemispheres, though the centre presiding 

 over the faculty of speech is placed in this part on the left side. 



As an objection to the soundness of these conclusions, the re- 

 markable and undoubted fact has been urged, that no matter how 

 thorough is the destruction of the centres, the function returns 

 after the lapse of a variable interval. In some instances the loss 

 of function only remains for a few hours after the operation ; in 

 other cases (those in which the injury is extensive and deep, and 

 the animal belongs to a class with high mental organization) the 

 recovery is slow and may extend over several weeks and months. 

 In man and monkeys the function may be lost forever, and the 

 nerve channels, which formerly carried the impulses to or from 

 the injured centre, become degenerated. 



From some of the foregoing facts viz., the constant and regu- 

 lar response of certain groups of muscles to the stimulation of 

 certain local spots of the brain surface, and the temporary destruc- 

 tion of the functions of some organ when a certain point is injured 

 it seems definitely fixed that certain local parts of the brain 



