352 "Journal of Comparative Neurology and Psychology. 



In this experiment No. 7 followed No. 2 from the first, standing 

 up beside him and getting in his way when he was pulling at the 

 knot. After No. 2 had opened the door, by pulling the knot, No. 

 7 generally would stay behind long enough to pull the knot him- 

 self before following No. 2 out. He did this sixteen out of the 

 twenty-seven times that No. 2 opened the door. When put back 

 alone No. 7 did not once try to get hold of the knot. He went to 

 the spot where the knot was and smelled of it and then ran to the 

 door. Apparently he did not see the knot for he acted similarly in 

 respect to the other parts of the cage. 



Experiment VII . Pulling a Bent Wire with the T^eth and Forepaws. 



Method. — In place of the knot used in the previous experiment, 

 a small piece of wire of the same size and color as the wire top was 

 used. The wire was bent at the end to make it easy for the rat 

 to grasp it with his teeth and paws. After being thoroughly 

 washed to remove all odor, the wire was suspended in the opposite 

 (not diagonally opposite) corner of the box to that where the knot 

 had been. It hung just on a level with the netting of the top, or 

 just low enough so that a rat could grasp it with his teeth without 

 first using his paws. In other respects the apparatus was just the 

 same as that used in the preceding experiment. 



Results. — February the second No. 2 was put in the box alone. 

 He first went to the spot where the knot had been and examined 

 it thoroughly. Then he began to try other places. In two min- 

 utes he had found the wire, pulled it, opening the door, and passed 

 out. Put back he first went to a spot halfway between where the 

 knot had been and where the wire was; then he went directly to 

 the wire, pulled it and passed out. Time, fifteen seconds. Put 

 back again he got out in ten seconds, although he first went to the 

 knot spot. The next two times he got out in eight seconds and yet 

 each time he first went to the spot where the knot had been before 

 going to the wire. The last time, since he went directly from 

 the door to the wire, he got out in three seconds. 



Nos. 3 and 4 were now put in the box together for fifteen min- 

 utes. They did not get out, neither did they pull the wire, 

 although they examined almost every other place in the box. 



