578 PHYSIOLOGY CHAP. 



vulsions do not involve all the muscles of the opposite side ; they 

 merely involve the muscular groups of which the centres are 

 intact, while those groups of which the centres have been excised 

 escape. 



(6) After destruction of the whole motor area on one side, 

 faradisation of the subjacent white matter, even with the strongest 

 currents, may fail to elicit true epileptic convulsions, though these 

 are readily evoked when the stimulation is applied to the cortex 

 of the motor area (Francois-Franck and Pitres, Fig. 295). 



(c) Occasionally, however, when the motor area on one side has 

 been extirpated, electrical stimulation of the subjacent white 

 matter may give rise to epilepsy. But in this case the convulsions 



A B 



YIG. 295. Curves from a dog's musclf i>roilurp<l l>y strong excitation. 



begin not in the muscles of the opposite side of the body, but in 

 those of the side excited. This shows that excitation of the white 

 matter produces the attack not through the bulb, but by trans- 

 mission of the excitation along association paths to the motor area 

 of the other hemisphere (Bubnoff and Heidenhain.) 



(d) This is confirmed by the fact that after bilateral extirpa- 

 tion of the motor zone electrical stimulation of the subjacent 

 medullary substance invariably fails to excite an epileptic attack, 

 no matter how strong the current (Bubnoff and Heidenhain). 



(e) If after incomplete extirpation of the motor area on one 

 side the portion left intact be stimulated, diffuse epileptic con- 

 vulsions may involve all the muscles, with the exception of 

 the groups represented in the area that had been destrovrd 

 (Uuverricht). 



(/) If during the initial phase of an epileptic attack produced 

 by laradising the motor area the sigmoid gyrus of the dog is 



