CEREBRAL FUNCTION IN THE RAT 113 



(experiment 29) developed an abnormal stereotyped reaction 

 to the situation and the other (experiment 33) was stuporous 

 during most of the tests so that the two animals scarcely pro- 

 vide data from which reliable conclusions can be drawn. With 

 the exception of these two and the questionable case described 

 in experiment 26, the animals with partial injuries to the frontal 

 pole gave clear evidence of retention of the habit. Among them 

 the one described in experiment 20 showed the most extensive 

 lesion, only the left mesial region being left intact (plate III, 

 fig. 20). In the others the lesions were more restricted, leaving 

 the frontal pole of one or other hemisphere intact. This sug- 



FIG. 11. TOTAL EXTENT OF LESION IN ANIMALS OF SERIES IV WHICH RETAINED 



THE HABIT 



gests the question whether or not there is some particular part 

 of the frontal region concerned with the retention of the habit. 

 Figure 11 shows the combined extent of the lesions in the 

 animals retaining the habit. Every part of the frontal region 

 was destroyed in one or another of the operations. 



It seems, then, that although some part of the frontal region 

 must remain intact if the plane-box habit acquired by the nor- 

 mal animals is to be retained, the particular part preserved is 

 immaterial. The different parts of the frontal region are, to 

 adopt a term from experimental embryology, equipotential in 

 the functioning of the habit. 



V. HABIT FORMATION AFTER DESTRUCTION OF LARGE AREAS OF 



THE CORTEX 



In spite of many dogmatic assertions concerning the function 

 of the cerebrum in so-called associative memory we have not a 

 single published account of any experiments which give con- 



P8YCHOBIOLOGY, VOL. I, NO. 2 



