LAS HLEY— CEREBRAL FUNCTION 265 



of this, the animal shifted to the use of his left hand in opening the 

 problem-boxes. Subsequent destruction of the greater part of the 

 corpus striatum did not produce a recurrence of the hemiplegic 

 symptom s. 



Number 3. — This was a large female rhesus trained on problem-boxes and 

 visual discrimination. After retention tests, the motor areas of both sides were 

 exposed, mapped and cauterized. Following the operation the legs and left 

 arm were completely paralyzed. The right arm made clumsy pawing move- 

 ments. Twelve hours after operation, the animal walked a few feet with stag- 

 gering gait, then collapsed with arms and legs widely extended, and for several 

 days made no further efforts to walk. The following day she grasped a grape 

 with her right hand and brought it to her mouth after several unsuccessful 

 trials. The movements were clumsy and slow. 



Four weeks after operation she seemed sufficiently recovered for retention 

 tests, although still showing a general clumsiness and marked weakness of the 

 left limbs. 



The average time per trial for successive groups of five trials in training, 

 preliminary retention tests and retention tests after operation is given in Table 3. 

 Visual discrimination was unaffected by the operation. 



Table 3. — Average Time in Seconds Per Trial Required for Opening Each 



Problem-Box in Each Day's Practice in Training, Preliminary Retention 



Tests, and Postoperative Retention Tests 



Pull Box Crank Box Hasp Box 

 1.0 2.2 49.2 



1.0 1.4 9.8 



2.6 1.4 8.4 



' Time with hasp unfastened. 



The time required to open the problem-boxes in the postoperative 

 retention tests gives certain evidence of the retention of the habits. 

 An average of 678.8 seconds was consumed in each of the first five 

 trials of training in opening the boxes by the method of random activity. 

 ( )nly 17.5 seconds' average were required for the first five trials of 

 the postoperative retention tests. The methods of opening the pull and 

 crank boxes were the same before and after the operation. The per- 

 sistent weakness of the left arm called for a change in method of open- 

 ing the hasp box. Before operation, the animal had used the same 

 method in twenty consecutive trials. The plug was pulled out of the 

 staple with the right hand. The hasp was lifted from the staple with 

 the right hand, turned back against the lid, and then transferred to the 

 left hand. The lid was lifted with the left hand and the right hand 



