I90 BRAINS OF RATS AND MEN 



was destroyed (usually by bilaterally symmetrical le- 

 sions), varying the operations so as to cover all regions 

 of the cortex in the total series of experiments. The 

 operated rats were then trained on the double-plat- 

 form box and their methods of learning compared 

 with those of normal animals. Figure 48 illustrates 

 the total field covered by these different operations in 

 the aggregate, showing that in one experiment or an- 



Fig. 48. — The total extent of bilateral cortical injury in all of the 

 rats subsequently trained on the double-platform box. After Lashley. 



Other the entire dorsal surface was explored and most 

 of the lateral surfaces. The archipallium (as in other 

 experiments) was not involved. 



These rats learned the habit as readily as normal 

 animals, indeed more quickly, in some cases in less 

 than half the normal number of trials. Some of these 

 cases parallel very closely the experiments of Lashley 

 and Franz (19 17) on the inclined plane box and show 

 that both of these problem-box habits can be learned 

 readily in the absence of the entire "motor cortex," or 

 of any other third of the cortex (except archipallium, 

 not tested). No details are given of the converse ex- 

 periment. It has been shown that a brightness-dis- 

 crimination habit can be learned after destruction of 



