272 ORIGINAL ARTICLES AND CLINICAL CASES 



cortex begins at the level of the thalamus as a narrow band and broadens 

 cephalad to include all of the cortex of the frontal pole. The lesion to the 

 corpus striatum extends from the caudal limit of the nucleus throughout its 

 length. All of the lateral half of the nucleus is destroyed, but the lesion 

 probably did not involve the median part in front of the anterior commissure. 

 The depth of the lesion is the same throughout its length, involving a little 

 more than the dorsal third of the corpus striatum. Left hemisphere : The 

 lesion to the cortex is practically identical with that on the right. The 

 greater part of the caudate nucleus is destroyed, only the extreme poles 

 remaining uninjured. 



This animal showed perfect retention to the visuo-motor habit after 

 nearly complete destruction of the motor areas. 



No. 24. Small adult male. — Trained in visual discrimination. One 

 hundred trials were required for learning with errors in successive tens of 

 trials distributed as follows : — 



4:5:3: 5:1:3:4:0:2:2: 0:0:0:0. 



The frontal pole was transected and the caudate nuclei cauterized. The 

 animal was stuporous for forty-eight hours after operation, then was tested for 

 discrimination. He reacted slowly, but found his way through the problem 

 box and gave some indication of discrimination, although he made frequent 

 errors. On the fourth day of the tests he began to discriminate accurately 

 and made no further errors. 



Post-operative retention tests ; errors in successive tens of trials :- — 



3:5:3:0:0:0:0. 



The fact that the habit was reacquired in thirty trials, in contrast to the 

 hundred of original training, shows retention rather than relearning. 



Extent of Unions (fig. 12). — Eight hemisphere. The lesion to the 

 cortex begins at the level of the anterior commissure and includes all of the 

 dorsal convexity of the frontal pole except a narrow median band. The hind 

 leg and part of the fore leg region remain intact. All of the caudate nucleus 

 in front of the anterior commissure is destroyed ; its posterior part is 

 uninjured. Left hemisphere: The lesion is almost identical with that on the 

 right. 



After extensive injuries to the stimulable area and destruction of 

 the anterior halves of both caudate nuclei this animal gave evidence of 

 retention. 



No. 25. Small adult female. — Trained in visual discrimination. One 

 hundred and ten trials were required for learning, with errors in successive 

 tens of trials distributed as follows : — 



4-5-4:5:2:3 -.5:3:1:1:1:0:0:0:0:0:0. 



The frontal pole was transected and the caudate nuclei cauterized. For 

 three days after operation the animal was unable to walk except in a very 

 narrow circle to the right and could not get through the problem box. On the 



