STUDIES OF CEREBRAL FUNCTION IN LEARNING 



271 



from the level of the anterior commissure to the base of the olfactory bulb, 

 destroying all of the cortex above this plane. All of the caudate nucleus in 

 front of the knee of the corpus callosum is degenerated ; the posterior part 

 is uninjured. 



This rat retained the visuo-motor habit after extensive but incom- 

 plete lesions to the stimulable cortex and caudate nuclei. 



No. 23. Small adult male. — Trained in visual discrimination. Forty 

 trials were required for learning, with errors in successive tens of trials dis- 

 tributed as follows : — 



7:5 : 2 : 4 : : : . 0:0:0:0:2:0:0:0. 



Fig. 11. — Extent of the lesions in No. 23. Arranged as in fig. 5. 



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

 three days after operation the animal's eyes were closed and he could not be 

 tested. On the fourth day he was in good condition and gave clear evidence 

 of discrimination. 



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



2:1:0:0:0. 



Extent of lesions (fig. 11). — -Right hemisphere: The lesion to the 



liKAIN- VOL. XI.'V. 



18 



