696 EFFECT OF STIMULI ON THE MOTOR CENTRES. 



attacks are never produced by stimulation of the surface of the posterior convolu- 

 tions. 



Strong stimulation of the motor regions may give rise in dogs to a complete general convul- 

 viv<- epileptic attack, winch usually begins with contractions ot the groups of muscles specially 

 related to the stimulated centre (Fcrrier, Euhnburg and Landois, Albcrtani, Lucxuni and 

 Tmmlmrini : then often passes to the corresponding limb of the opposite side (associated move- 

 ment^ : and lastly, a)l the muscles of the body are thrown into tonic and then into clonic 

 Mama The opposite 8"ie of the body has been observed to pass into spasm from below up- 

 wards after the contractions were developed in the other side. The spasmodic excitement 

 passes' from centre to centre, an intermediate motor region never being passed over. After this 

 condition has once been produced, the slightest stimulation may suffice to bring on a new 

 epileptic attack ( 373). During the attack, the cerebral circulation is accelerated. According 

 to Eckhaid and Danillo, epileptic attacks cannot be discharged from the posterior part of the 

 cerebrum by means of weak currents. Stimulation of the subcortical white matter causes 

 epilepsy, which, however, begins in the muscles of the same side {Bubnoff and Heidenham). 

 These contractions are due to an escape of the electrical current, which thus reaches the medulla 

 oblongata ( 373). - '< 



If certain motor areas are extirpated, the epileptic attack is absent from the muscles con- 

 trolled by these areas (Luciani). Separation of the motor cortical area by means of a horizontal 

 section during an attack cuts short the latter (Munk). During an epileptic attack it is possible 

 to excise the inotor area of one extremity, and thus exclude this limb from the attack whilst the 

 rest of the body is convulsed. 



Drugs. The continued use of potassium bromide prevents the production of epilepsy on stimu- 

 lating the cortical areas. 



Chsmical Stimulation. Substances such as occur in urine, e.g., kreatinin, 

 kreatin, acid potassic phosphate, and sediment of urates, when sprinkled on the 

 motor areas of the dog, cause pronounced eclampsic, clonic convulsions, which recur 

 spontaneously, and are followed by deep coma. These symptoms are like those of 

 anemic poisoning. The sensory centres, especially that for vision, seem also to be 

 affected by chemical stimulation [Landois). 



[Motor Centres in the Monkey. Ferrier has mapped out a large number 

 of centres on the outer surface of the brain in the monkey, and to each centre he 

 has given a number. These numbers have been transferred to corresponding con- 

 volutions on the human brain, numbered accordingly. These areas are specially 

 distributed on the convolutions around the fissure of Rolando, including in the 

 monkey, the posterior extremities of the posterior and middle frontal convolutions, 

 the ascending frontal, ascending parietal, and part of the parietal lobule.] 



[Fi<j. 484 represents these areas transferred to the corresponding areas in man. (1) On the 

 superior parietal lobule (advance of the opposite hind limb, as in walking). (2), (3), (4) Around 

 the upper extremity of the fissure of Rolando, (complex movements of the opposite leg and arm, 

 and of the trunk, as in swimming), (a), (b), (c), (d), On the ascending parietal or posterior 

 central convolution (individual and combined movements of the fingers and wrist of the opposite 

 hand or prehensile movements). (5) Posterior end of the superior frontal convolution (exten- 

 sion forward of the opposite arm and hand). (6) Upper part of the ascending frontal or anterior 

 central convolution (supination and flexion of the opposite fore-arm). (7) Middle of the same 

 convolution (retraction and elevation of the opposite angle of the mouth). (8) At the lower 

 end of the same convolution (elevation of the ala nasi and upper lip, and depression of the 

 lower lip on the opposite side). (9), (10) Broca's convolution (opening of the mouth with pro- 

 trusion and retraction of the tongue aphasic region). (11) Between 10 and the lower end of 

 the ascendiug parietal convolution (retraction of the opposite angle of the mouth, the head 

 turns towards one side). (12) Posterior part of the superior and middle frontal convolu- 

 tions (the eyes open widely, the pupils dilate, and the head and eyes turn towards the 

 opposite side). (13), (13') Supra-marginal and angular gyrus (the eyes move towards the 

 opposite side, and upwards or downwards centre of vision). (14) Superior temporo-sphenoidal 

 convolution (pricking of the opposite ear, pupils dilate, and the head and eyes turn to the 

 opposite side hearing centre).] 



[Experiments on Monkeys. Electrical stimulation of the anterior part of the 

 frontal lobes yields negative results; but behind the anterior end of the sagittal 

 limb of the precentral sulcus, there are lateral movements of the head and eyes. 

 If the anterior third or fourth be removed, Schafer and Horsley observed no motor 



