The localization of parts of the brain which govern particular 

 movements was first established by Hughlings Jackson's investigation 

 of those cases of epilepsy in which the spasm begins in some parti- 

 cular part, and spreads in a definite order to the other parts of the 

 body. The fits are generally preceded by a sensation in the part 

 where the spasm begins the aura. Many such cases have been 

 operated on, the motor centres localized by electric excitation and 

 the offending centre removed. The results thus obtained in man 

 confirm the observations made on the chimpanzee and gorilla. The 

 motor area of the chimpanzee is shown in the accompanying 

 figures. On the outer side it occupies chiefly the precentral 



Foot & Toes 



Knee 

 Hip,. 

 Shoulde 

 Elbow^ 

 Written Speech^ 



Hand 

 Index- 

 Thumb 



Upper 



Face 



Lower . 

 Face 



Motor _ . 

 Speech 

 Tongue- - 

 Larynx- 



Movements of 

 ye(probable) Taste 



and., , 

 Smell ' 



Great Toe 



Tactile & Muscular sensation 



Visual word, 

 Memory 



Hearing, 

 uditory word 

 Memory 



alf Vision centre 



FIG. 4,38. LEFT HEMISPHERE, SHOWING SITUATION OP THE HUMAN CORTICAL 

 PROJECTION CENTRES. (Mott.) 



convolution in front of the fissure of Rolando ; it overlaps slightly 

 on the inner side of the hemisphere. The localization corresponds in 

 a reverse order to the distribution of the spinal nerves. The order is 

 perineum ; up the leg toes, ankle, knee, hip ; trunk ; down the arm 

 shoulder, elbow, wrist, fingers; neck; movements of mouth, tongue, 

 etc. Eye movements are situated farther forward in the frontal region. 



The Effects of Ablation of the Motor Area. If one of the motor 

 areas be removed, there results a paralysis of voluntary movements 

 in the corresponding part of the body on the opposite side. In the 

 dog this paralysis almost wholly passes off ; in the ape to a less degree ; 

 while in man the degree of recovery is very limited. So much is this 

 the case that the site of a brain lesion can be diagnosed during life, 

 and verified after death. Even in man there is a certain amount of 

 recovery, especially of limb movements made in association with the 

 other limbs. Accompanying the loss of movement is a diminution 

 in the sensibility, particularly in regard to the position of the part. 

 For example, a man whose arm centre has been excised does not 

 know the position of the limb, or how much it has been passively 



46 



