274 



ORIGINAL ARTICLES AND CLINICAL CASES 



were destroyed in this animal. There was clear evidence of retention 

 following the operation. 



This group of animals is not selected, but comprises all that 

 survived the operation long enough to allow of retention tests. Every 

 one of them gave evidence of retention early in the tests. Table I 

 gives the number of trials and the number of errors, in learning and 

 and in the post-operative retention tests. The average number of 

 trials required for learning is eighty. Only 33*3 trials on the average 



Pig. 13. — Extent of the lesions in No. 25. Arranged as in fig. 5. 



were required after operation to reach the same degree of accuracy in 

 discrimination. Errors were made in an average of 26'6 trials in 

 learning and in only 6'3 trials in the retention tests. These figures 

 include errors obviously due to motor disturbance and fright following 

 operation. Thus, No. 21 was never able to turn directly to the left 

 and all her errors seemed due to failure to compensate for the motor 

 difficulty ; No. 24 was slow and stuporous during the time when 

 errors were made ; six of the eight errors made by No. 25 were made 



