I70 BRAINS OF RATS AND MEN 



number of trials as in the first learning, and the rats 

 which had been overtrained by more than twelve 

 hundred trials did not reacquire the habit with more 

 facility than did those which had received no over- 

 training. "There is no indication that subcortical nu- 

 clei have taken over any part of the reaction, even 

 sufficient to facilitate relearning" (1921, p. 465). 



4. Does cerebral injury give rise to disturbances 

 in the general reactions of the rat such as would inter- 

 fere seriously with learning, even though the essential 

 structures for learning were still intact? 



It is well known that complete or nearly complete 

 decerebration in opossums (Rogers, 1924), dogs 

 (Goltz, 1892; Rothmann, 1923; Dresel, 1924), and 

 men (Edinger and Fisher, 1913), results in profound 

 depression or stupor, alternating perhaps with de- 

 cerebrate restlessness and loss of most of the complex 

 habits. None of the rats studied were completely de- 

 cerebrated, so that we do not know what the effect of 

 this operation upon this animal really is. The partial 

 operations may also have an effect on general vigor, 

 motility, or specific sensori-motor reactions which 

 affect the learning process, and this question was 

 especially studied (1920, p. 68). 



Normal animals and those with various partial 

 destructions of the cerebral cortex were put into re- 

 volving cages so arranged as to record the revolutions 

 on a kymograph. In this way the total activity of the 

 different rats for twenty-four-hour periods could be 



