THE CEREBRUM 



character that they may be regarded as identical with those produced by 

 volitional effort, while destruction of these areas is followed by a loss of 

 motion or paralysis of these muscles. Collectively these areas are known as 

 motor areas and are as follows : 

 i. A head and eye area. 



A face area. 



An arm area. 



A trunk area. 



A leg area. 



The location of these areas will be apparent from an examination of Figs. 

 248 and 249. 



FIG 248 DIAGRAM OF THE MOTOR AND SENSOR AREAS ON THE LATERAL SURFACE OF 

 THE MONKEY BRAIN. (After Horsley and Schdfer.) 



Motor Reactions Following Electric Stimulation of Sensor Areas.- 



Electric stimulation of the sensor areas is attended by certain motor reac- 

 tions which vary in accordance with the area stimulated Thus, wh< 

 electrodes are applied to different portions of the occipital lobe the eyeballs 

 are coniugately turned upward, downward, or laterally and to the opposite 

 side; when placed on the upper portion of the superior temporal convolu- 

 tion the ear is pricked up or retracted, the head is turned to the opposite 

 side' and the pupils are dilated; when placed on the hippocampal convolu- 

 tion there is movement of torsion of the nostril and lips of the same side_ 

 was then assumed that the movements were reflex m character inasmuch 

 as they resembled the movements caused by strong impressions mad, 

 sense organs and due to the development of sensations by the electric cu 

 ren s and not an evidence that the area in question is a motor area in the 

 sense that this term is applied to the area along the Rolandic fissure especially 



s their destruction is not followed by paralysis of any of the corresponding 

 muscl s The vlw that these reactions are reflex in character has been 



Tstantiated I by the anatomic fact that in the immediate neighborhood of 

 each sense area though not overlapping it, motor cells are present from 

 whth fferen nerve-fibers pass in close relation to the afferent fibers toward 

 Tnd to lower nerve-centers and presumably to the centers of origin of related 



