1 88 BRAINS OF RATS AND MEN 



We have now reviewed the positive evidence for 

 cortical localization in the rat. On the negative side of 

 the question there are some experiments which tend to 

 obscure the significance of this evidence and even to 

 suggest that the rat's cortex, in some of its functional 

 aspects at least, acts in a non-specific way with no de- 

 monstrable localization. This evidence must next be 

 examined. 



In the first place, it has already been mentioned 

 that in the case of simple maze-learning there is no 

 evidence for any cortical localization of either acquisi- 

 tion or retention of this habit or indeed for cortical 

 participation of any sort. The habit is learned in the 

 absence of any third of the cortex with normal ease, 

 and it is retained after destruction of any third of the 

 cortex. What effect upon this habit is produced by 

 total destruction of the cortex has not been deter- 

 mined. This case is very different from that of the 

 brightness-discrimination habit which has a specific 

 relation of some sort with the visual area in the occipi- 

 tal region and the inclined plane latch-box which is 

 related with the frontal region. 



In another series of experiments (1920) on kines- 

 thetic-motor habits a different apparatus was em- 

 ployed — a double-platform latch-box (Fig. 47). The 

 rat must first depress the platform a and then the 

 platform b before the door of the food-box is opened. 

 This is a more complicated reaction than that re- 

 quired to open the inclined plane box used in the earli- 



