CEREBRAL FUNCTION IN THE RAT 85 



and others with almost identical lesions made several errors. 

 This lack of relation between the extent of frontal lesion and 

 the degree of retention provides further evidence that the func- 

 tioning of the maze-habit is independent of the frontal region of 

 the cortex. 



II. THE RETENTION OF THE MAZE-HABIT AFTER FRONTAL AND 

 TEMPORAL OR FRONTAL AND OCCIPITAL LESIONS 



Experiment 15. After retention had been tested in the animals 

 described in experiments 8, 9, 10, 11, 12 and 13 they were allowed 

 to rest for two weeks and then were retrained for twenty-five 

 trials, showing practically no loss of the habit in this time. 

 They were next subjected to a second operation. In three, an 

 incision was made from the locus of the first operation backward 



FIG. 3. TOTAL EXTENT OF THE LESIONS IN ANIMALS OF SERIES II, WHICH 

 RETAINED THE MAZE-HABIT AFTER THE SECOND OPERATION 



on both sides for a distance of 5 mm. In the other three the 

 scalpel was passed almost horizontally backward through the 

 cortex of the dorsal convexity from the region of the first lesion 

 to the tentorium. Three of these animals survived, one after, 

 occipital lesion (11) and two after temporal lesion (10 and 12). 

 The lesions have been defined in the descriptions of these ani- 

 mals and figured in plate II, figures 10, 11, and 12. The com- 

 bined extent of the lesions is shown in figure 3. 



All three animals showed perfect retention of the habit after 

 the second operation. They were each given fifteen trials in the 

 maze on the day following the second operation, and ten trials 

 on the second day. Number 10 averaged 2.5 seconds per trial 

 in these twenty-five trials and made only one error. Number 

 12 averaged 2.6 seconds and made one error in the same number 



