THE CEREBRUM. 



499 



lines more closely resembles that of man than does the brain of any 

 other animal. The results therefore which are obtained, there is 

 every reason to believe, are the results, in their general outlines, that 

 would follow stimulation of the human brain if this were possible 

 under the same condi- 

 tions. Indeed, the clinical 

 symptoms which arise 

 during the development 

 of pathologic processes, 

 and the phenomena 

 which occur during sur- 

 gical procedures for the 

 removal of growths and 

 pathologic cortical areas, 

 justify the conclusion 

 that the chart of the 

 motor and sensor areas 

 of the monkey brain may 

 be transferred to the 

 human brain without 

 introducing any serious 

 errors. 



The Motor Areas of 

 the Monkey Brain. 

 From experiments made 

 on the brains of monkeys 

 Ferrier mapped out a 

 number of areas stimu- 

 lation of which gives 

 rise to muscle contrac- 

 tions on the opposite 

 side of the body which 

 are so purposive and co- 

 ordinate in character that 

 they may be regarded 

 as identical with those 

 produced volitionally. 

 Destruction of these 

 areas is followed by 

 paralysis. The results of Ferrier's earlier work are represented in 

 Fig. 223, the descriptive text to which renders them intelligible. In 

 a general way it may be said that^the upper third of the anterior and 

 posterior central convolutions presides over the movements of the leg 

 of the opposite side of the body; the middle third over the move- 

 ments of the arm; the inferior third over the movements of the 



FIG. 223. LEFT HEMISPHERE or MONKEY, SHOW- 

 ING DETAILS OF MOTOR AREAS INDICATED BY 

 THE MOVEMENTS FOLLOWING STIMULATION 

 OF: i. Superior parietal lobule; exciting ad- 

 vance of the hind limb. 2. Top of ascending 

 frontal and parietal convolutions; flexion and 

 outward rotation of thigh; flexion of toes. 3. 

 On ascending frontal convolution near semilu- 

 nar sulcus; movements of hind limb, tail and 

 extremity of trunk. 4. On adjacent margins of 

 ascending frontal and parietal convolution; 

 adduction and extension of arm, pronation of 

 hand. 5. Top of ascending frontal near supe- 

 rior frontal convolution; forward extension of 

 arm. a, b, c, d. On ascending parietal; move- 

 ments of various muscles of the forearm. 6. 

 Ascending frontal convolution; flexion of 

 forearm and supination of hand which is 

 brought toward mouth. 7. Retraction and 

 elevation of corner of mouth. 8. Elevation of 

 nose and lip. 9 and 10. Opening mouth and 

 motions of tongue, n. Retraction of angle 

 of mouth. 12. Middle and superior frontal 

 convolutions; movements of head and eyelids. 

 13 and 13'. Anterior and posterior limbs of 

 angular gyrus; movements of eyeballs. 14. 

 Superior temporo-sphenoidal convolution, ear 

 pricked and head moved. 15. Movement of 

 lip and nostril. (Ferrier.} 



