THE FORE-BRAIN 



557 



Horsley, since they found that* the motor area does not extend to 

 the postcentral convolution, but is confined to the whole extent of 

 the precentral and the introflexed cortex of the Rolandic sulcus, 

 and that the excitable areas of which it consists are not separated 

 from one another by intermediate inexcitable spots, but partially 

 overlap at the margins, forming a true continuous excitable zone, 

 like that observed on the lower apes. 



It is remarkable that the topographical distribution of the 

 cortical centres for the musculature of the different reions of the 



Sale. Central. Antj , * 



Sulc.precenbr.marg. 



Sulc.calcarin. 



FIG. 282. Internal or mesial surface of brain of orang, showing excitable areas. 

 (Grunbaum and Sherrington.) 



body lies within fairly exact limits along the precentral con- 

 volution, from below upward, in the segmental bulbo-spinal order 

 (Fig. 281). 



In man, too, observations have been made with the object of 

 mapping out the topography of the excitable areas of the 

 cortex. The first attempts were made by the American surgeon 

 Bartholow and the Italian neurologist Sciamanna. But the data 

 obtained were scanty, since only very circumscribed areas of the 

 cortex, exposed by surgical operations, were excited. More 

 recently, owing to the progress of cerebral surgery, the Rolandic 

 region of the human brain has often been exposed in cases of 

 epilepsy, and excited by the same faradisation "methods as are 

 employed in dogs and monkeys. The most important results 

 were obtained by Ferrier in four individuals (1890), by Horsley 



