CEREBRAL LOCALIZATION 849 



will exclude the corresponding muscular area from participation in 

 the fit. 



CLINICAL OBSERVATIONS 



The foregoing results obtained by experimental stimulation in animals, 

 are very similar to the symptoms observed in man when the cerebral 

 cortex is stimulated by the pressure on it of a meningeal tumor or a 

 spicule of bone. Such stimulation causes contraction in the correspond- 

 ing muscular area; the contraction then spreads to neighboring groups 

 of muscles, and may ultimately involve the whole musculature of the 

 body in a convulsive fit, like that produced in animals. This is known 

 as Jacksonian epilepsy, and it is to be distinguished from ordinary 

 epilepsy by the fact that the patient does not become unconscious dur- 

 ing the fit. Like ordinary epilepsy, however, the Jacksonian' type is 

 usually preceded by a peculiar sensation of numbness or tingling in the 

 area that is to show the first contraction. One of the greatest achieve- 

 ments of modern brain surgery is the cure of Jacksonian epilepsy, by 

 trephining the skull over the affected center and removing the meningeal 

 tumor or spicule of bone which is responsible for the stimulation. To 

 enable the surgeon to locate exactly the position of the irritating body, 

 it is necessary to examine the patient very closely as to the muscular 

 group which is initially affected during the convulsions, and then to 

 examine an outline map of the cerebral hemisphere indicating the po- 

 sition of the various motor and sensory areas as deduced mainly from 

 experiments on the higher monkeys and verified by the experience 

 gained by previous operations. Topographic maps indicating the sur- 

 face markings corresponding to the various convolutions of the cerebrum 

 must also be used. In such operations the surgeon often has the op- 

 portunity of experimentally verifying the position of various centers. 



