CONVOLUTIONS AND FISSURES OF SURFACE OF CEREBRUM. 59 



toms of degeneration. The symptoms of irritation are shown 

 by convulsive movements ; the symptoms of degeneration by a 

 greater or less inability to set the muscles in motion at will, 

 oftentimes only in a sense of weakness, or by awkwardness in 

 executing some complicated movement. 



From careful analysis of known cases of disease, it is cer- 

 tain that, in injury of the upper part of both central convolutions 

 and the paracentral lobule, the motor disturbances are most 



FIG. 36. 

 Lateral view of brain. The "motor region" shaded. (After Exner.) 



prominent in the legs, that when the lower end of the central 

 convolutions is involved the regions supplied by the facial and 

 hypoglossus suffer most, and that motor disturbance of the 

 upper extremities follows when the middle and a part of the 

 upper third of these convolutions are involved. The divisions 

 between these separate " centres " are not sharply drawn. 



Complete destruction of separate portions of the cortex in 

 the human being may lead to permanent paralysis of the muscles 



