18 



K. S. LASHLEY 



112, are summarized in table 4. The lesions are shown in 

 plate 8, figures 103 to 112. The total range of the lesions is 

 shown in text figure 3. The average extent of the lesions in 

 these cases is 25.9 ± 1.5 per cent of the neopallium. For 

 learning they required an average of 146.0 ± 8.8 trials with 

 41.7 ±: 2.9 errors. In the preliminary retention tests they 

 made an average of 4.8 errors. For relearning after opera- 

 tion they required an average of 93.0 ± 9.5 trials with 20.4 ± 

 2.1 errors. 



TABLE 4 



Data for group C, trained iefore operation with postoperative retention tests 



fourteen days after operation. Arranged as table 3 



Group D. Cases with lesions to the thalamus. One case, 

 no. 49 (fig. 49), was obtained with extensive lesions in the 

 optic nuclei of the thalamus, followed by initial training. This 

 animal required 280 trials for learning, with 132 errors. The 

 percentage of the neopallium destroyed was 25.2, with prac- 

 tically all of the hippocampus degenerated and with some 

 injury to the superior colliculi. 



Four cases with injury to the thalamus after training were 

 obtained. These were nos. 99, 100, 101, and 102. They re- 

 quired an average of 167.5 trials for learning, with 36.2 errors. 

 In preliminary retention tests they averaged 1.7 errors. In 

 postoperative tests they required 152.0 trials, with 54.2 errors. 



