THE CENTRAL NERVOUS SYSTEM 



743 



found the most suitable form of stimulus (see Practical Exercises, 

 p. 769). For certain purposes the method of Ewald has advantages. 

 He fixes in a trephine hole in the skull an ivory plug, through which 

 pass the electrodes. When the animal has recovered from the 

 operation, the region of the brain in contact with the electrodes can 

 be stimulated without fastening the animal. 



Motor Areas. Lying around the fissure of Rolando, and 

 lapping over on the mesial surface of the hemisphere in this 

 region, are the so-called motor areas (Figs. 264 to 270). 

 They occupy the 

 whole of the ascend- 

 ing frontal and pa- 

 rietal convolutions, ^ j 



* t -.-... 

 f 



$>. 



running forward a 

 little into the hori- 

 zontal frontal con- 

 volutions, backward 

 a little into the 

 superior parietal con- 

 volution, and turning 

 over on the mesial 

 surface into the mar- 

 ginal convolution. 



Highest of all on the 



, . FIG. 265. DOGS BRAIN WITH LESION. 



convexity of the hemi- A portion of the cortex indicated by the shaded area 



Sphere lies the area was destroyed by cauterization. The symptoms were 



*. complete blindness of the opposite eye (in this case the 



of the leg ; belOW right) ; weakness of the muscles of the limbs and of the 



. , . . j ,i neck on the right side ; slight weakness of the limbs on 



thlS, in Order, the the left side . When the animal wafted there was a 



ot-ooc fr\r tViA arm tendency to turn to the left in a circle. In eating or 



d11 J > drinking the head was turned to the left, so that the 



face, mOUth. pharynx, mouth was oblique, and the right angle of the mouth 



was lower than the left. The tail movements were 



and larynx. In front normal, and there was no deviation of the tail to one 



of the leg and arm side ' 



areas lies the area of the head, neck, and eyes, passing out 

 into the posterior portions of the first and second frontal 

 convolutions. On the mesial surface in the marginal con- 

 volution lie areas for the head, arm, trunk, and leg in order 

 from before backwards. 



It is to be particularly noted (i) that within the larger 

 areas, such as those of the arm and leg, smaller foci can be 

 mapped off which are related to movements of the separate 



