2I-.K 



ORIGINAL ARTICLES AND CLINICAL CASES 



destruction of almost the entire stimulable cortex and of the posterior 

 two-thirds of both caudate nuclei. 



No. 21. Small female about 90 days old. — Trained in visual discrimina- 

 tion. Ninety trials were required for learning, with errors in successive tens 

 of trials distributed as follows : — 



8:5:5:3:2:3:0:4:1:0:0:0:1:1:0:0:0. 



The frontal lobes were transected and the caudate nuclei cauterized. For 

 the first week after operation the animal was unable to walk except in 6-inch 

 circles and could not make her way through the discrimination box. By the 



Fig. 8.— Extent of the lesions in No. 20. Arranged as in fig. 5. 



ninth day after operation the motor disturbance had cleared up so that she 

 could walk without rotation, although she still rotated when attempting to 

 change direction and could not turn her body to the left. Eetention tests 

 were begun at this time and the animal at once gave certain evidence of 

 discrimination. The tests were continued for twelve days. Throughout this 

 tune siie was unable to turn to the left but compensated by rotating 270 

 degrees to the right wherever the problem box demanded a turn of 90 



