58 Animal Intelligence 
a point about 15 inches high and 6 inches in from the 
right edge of the front. We may call M ‘Lever outside.’ 
| 
(3inZ 
J 
SinZ. 2]. 
6mZ Z 
Fic. 13. 
N was a pen 5X3 feet made of wire netting 46 inches 
high. The door, 31 X 20, was in the right half of the front. 
A string from the bolt passed up over a pulley and back to 
the back center, where it was fastened 33 inches above the 
floor. Biting or pawing this string opened the door. 
