THE BRAIN. 



509 



the will as well as the conscious center, and when largely diseased 

 or destroyed, the only movements made are involuntary, depending 

 on other nerve-centers. 



Cerebral Localization. Although the study of the intellectual 

 faculties is both difficult and abstruse, much advance has in late 

 years been made in the knowledge of the physiology of the cere- 

 brum, so far as relates to the production of voluntary movements 

 and the reception of sensation. Observations upon both man and 

 the lower animals have led to the belief that the power of pro- 

 ducing certain movements is limited to certain restricted areas of 

 the brain, and that other areas are connected with sensation. 



Lobulus paracentralis, 



FIG. 299. Lateral view of the brain : gyri and lobuli marked with antique type, 

 the sulci and fissures with italic type (from Ecker). 



These are known respectively as motor, sensorimotor, or Icinesthetic 

 or Rolandic areas, and sensory areas. The localizing of these 

 functions is cerebral localization. 



These observations had their beginning in 1870. It was found 

 that when galvanic currents were applied to certain parts of the 

 cerebral convolutions movements of particular muscles followed, 

 and that in order to excite these muscles these parts or areas must 

 be stimulated. Although the dog was first experimented upon, 

 other animals (cat, rabbit, and monkey) have furnished like results. 

 In the application of these experiments the animal is put under 

 ether, the skull is trephined, and the poles of a galvanic battery 

 are applied to the convolutions. When on such stimulation of a 



