STUDIES OF CEREBRAL FUNCTION IN LEARNING. VII 15 



and loci of the lesions are shown in the appended plates. In 

 the tables and plates the cases are numbered serially and 

 arranged for each group in the order of the magnitude of 

 the lesions. 



Group A. Animals with training after injury in the occipi- 

 tal region, to determine the effects of injury upon the rate of 

 initial learning. The cases, numbered from 1 to 48, inclusive, 

 are summarized in table 2. The diagrams in figures 1 to 48 

 represent the cerebral lesions in the animals bearing the 

 corresponding numbers. The total area covered by all the 

 lesions is shown in text figure 1. 



The lesions range in extent from 3.5 to 43.9 per cent of the 

 total neopallium, with an average of 17.9 ± 0.9 per cent. For 

 learning the animals of this group required an average of 

 121.9 ± 4.5 trials, with an average of 39.1 ± 1-6 errors made 

 during training. 



Group B. Animals with initial training before brain injury. 

 Preliminary retention tests at an interval of seven days, fol- 

 lowed immediately by operation. Postoperative retention 

 tests seven days after operation. These cases are summarized 

 in table 3, numbered from 50 to 98, inclusive. The diagrams 

 of the lesions, bearing the corresponding numbers, are shown 

 in figures 50 to 98, inclusive. The total range of the lesions 

 is shown in text figure 2. 



The lesions range in extent from 1.5 to 31.9 per cent of the 

 total extent of the neopallium, with an average of 15.8 ± 0.7 

 per cent. For initial learning before operation these ani- 

 mals required an average of 128.2 ± 5.2 trials, with 41.8 ± 2.5 

 errors made during training. In the preliminary retention 

 tests they made an average of 1.4 errors. For relearning 

 after operation they required an average of 44.6 ±: 3.4 trials, 

 with 13.7 ± 1.2 errors, or about one-third as many as in initial 

 learning. 



Group C. Animals trained before operation with prelimi- 

 nary retention tests after fourteen days. Operation followed 

 these tests immediately and postoperative tests fourteen days 

 after operation. Data on these cases, numbered from 103 to 



THE JOURNAL OP COMPARATIVE NEUBOLOGT, VOL. 41, NO. 1 



