10 



S. I. FRANZ AND K. S. LASHLEY 



first corner after passing the turn he would pause with his nose close 

 in the corner (but without apparent sniffing), then back away and turn 

 down the alley to the food. Tests made by pulling his vibrissae while 

 he was eating indicated that these organs were lacking in tactile sen- 

 sitivity. The records of learning and retention were the following. 



Experiment 5. Fl 9 . Seventy-five days old. Learning was com- 

 pleted in 90 trials with 10 trials per day. Training was continued for 

 120 trials. 



Operation through a single small trephine hole on the left with little 

 hemorrhage. Retention was tested twenty-six hours later. The rat 

 oriented in the starting compartment, and in the majority of trials fol- 

 lowed the path indicated in figure 1. On the third and fifth trials she 

 retraced a part of the direct pathway to the food and on the tenth trial 

 she swerved so that her head was in the cul de sac but she never ven- 

 tured entirely off the direct pathway. The records of learning and 

 retention were the following. 



Experiment 6 '. F2cf. Sixty-nine days old. Learning was completed 

 in 24 trials with 2 trials per day. Training was continued for 170 

 trials. 



Operation through large transverse opening with very severe hemor- 

 rhage. Retention was tested twenty-three hours after the operation. 

 The rat was active and oriented correctly in the starting compartment. 

 In four trials the rat returned to the starting compartment after ad- 



