644 PHYSIOLOGY OF THE CEREBRUM 



teach him a whole series of complicated movements which gave evidence of his 

 intelligence. However, he showed also a considerable number of disturbances 

 of the motor mechanisms, among which may be mentioned especially his in- 

 ability to perform isolated movements with only one extremity. Besides, his 

 movements were excessive and were done with a waste of energy ; and there was 

 no proper gradation of them e. g., in order to extend his paw, he was compelled 

 first to sit upright and then to give both paws at the same time in a rather 

 sudden and explosive manner. 



From these and other experiments of the kind it appears that the move- 

 ments of the dog, including those which must be regarded as intentional and 

 conscious, can be carried out without the cooperation of the motor areas; 

 but that on the other hand, the finer regulation of these movements is for 

 the most part destroyed by extirpation of the corresponding areas. It would 

 follow that in the dog the motor cortical areas are really necessary only for 

 the nicer regulation of movements. 



Horsley and Schafer observed the following phenomena after extirpation 

 of the cortical areas from the monkey (Macacus). If the whole excitable 

 region on the convex side of the hemisphere were extirpated and only the 

 median cortical region left, there was exhibited an almost complete paralysis 

 of the opposite arm, paralysis of the facial muscles, weakness in the muscles 

 of the posterior extremities, and a greater or less difficulty in moving the 

 head toward the opposite side. The muscles of the trunk were unaffected, 

 and the weakness in the posterior extremity was not so great that the animal 

 could not use it in walking and climbing. 



When only a part of the excitable region on the convex surface of the 

 hemisphere was destroyed e. g., the field for the wrist and fingers a perma- 

 nent weakness appeared in these muscles while the other muscles were mov- 

 able in a perfectly normal fashion. In the same way destruction of the 

 cortical field of the arm produced paralysis of the arm without any disturb- 

 ance in the movements of the face, head, trunk or posterior extremity. When 

 the destruction of the field was complete, paralysis of the corresponding 

 muscles appeared to be permanent. But when a part of the field was left 

 behind the ability to move the parts returned to a certain extent. 



The consequences of destroying the motor region on the medial side are 

 worthy of note. Following bilateral destruction of this region there was 

 complete paralysis of the muscles of the trunk, a certain weakness in those 

 of the arms and a very extensive paralysis in the muscles of the posterior 

 extremities. The weakness in the arms involved mainly certain shoulder 

 muscles, especially those which draw the shoulder blade upward and back- 

 ward ; it was less marked in the muscles of the arm and forearm, and scarcely 

 or not at all noticeable in the finger muscles. Paralysis of the posterior 

 extremities extended to almost all the muscles, only a few flexors of the hip 

 joint being exempt. 



By practice the monkey, like the dog, can acquire the use of muscles 

 corresponding to the extirpated cortical fields; can learn, in other words, 

 to execute intentional movements with them. 



Hering, Jr., found that the cortical fields, electrical stimulation of which 

 gave movements of the forearm, including grasping movements, could be entirely 





