RETENTION OF HABITS BY THE RAT 



11 



vancing for his own length into the middle alley, but he did not leave 

 the pathway once in fifteen trials. The records of learning and re- 

 tention follow. 



Experiment 7. G3cf. Seventy-three days old. Learning was com- 

 pleted in 24 trials with 10 trials per day. Training was continued 

 for 170 trials. 



Operation through two trephine holes with little hemorrhage. Re- 

 tention was tested twenty hours after the operation. He oriented 

 correctly to the opening of the door, ran quickly and followed the path 

 of figure 1 in all but the first and second trials. In the first trial he 

 entered the cul de sac but turned back without exploratory sniffing. 

 In the second trial he put his head into the entrance of the cul de sac, 

 but did not enter it. He appeared to be anosmic. The records of 

 learning and retention follow. 



Experiment 8. F2 9 . Seventy-five days old. Learning was com- 

 pleted in 25 trials with 2 trials per day. Training was continued for 

 200 trials. 



Operation by transverse opening with severe hemorrhage. Re- 

 tention was tested twenty-six hours after the operation. The rat was 

 very weak and her movements were as a rule, slow and hesitating but 

 without marked pauses at the entrance of the cul de sac. On the first 

 trial she explored the cul de sac quickly, but without exploratory snif- 

 fing, and had some difficulty in finding the food in the dish. On the 



