The Mental Life of the Monkeys 179 



Box SS (triple; wood-plug, hook and bar) was a box 

 about the size of BB. To open the door, a bar had to be 

 pushed around, a hook unhooked and a plug removed from 

 a hole in the top of the box. 



Box TT (nail plug) was 14 by 10 by 10 inches with a door 

 5.5 by 10 on the right side of the front, the rest of the front 

 being barred up. The door was hinged at the bottom and 

 fastened at its top to a wire which was fastened to a nail 

 2.5 inches long, which, when inserted in a hole 0.25 inches 

 in diameter at the back of the top of the box, held the door 

 closed. By drawing out this nail and pulling the door 

 the animal could open the door. 



Box VV (plug at side) was a box about 18 by 10 by 10, 

 the door held by a plug passing through a hole in the side 

 of the box. When the plug was pulled out, the door could 

 be pushed inward. 



Box W (loop) was 17 by 10 by 10 inches with a door 5 by 9 

 at the left side of its front hinged at the bottom. The door 

 was prevented from falling inward by a wire stretched 

 behind it. It was prevented from falling outward by a 

 wire firmly fastened at the right side and held by a loop over 

 a nail at the left. By pulling the loop outward and to the 

 left it could be freed from the nail. The door could then 

 be pulled open. 



Box WW (bar inside) was 1 6 by 14 by 10 inches with a 

 door 4 by ii at the left of its front hinged at the bottom. 

 The door could be pushed in or pulled out when a bar on 

 its inside was lifted out of a latch. The bar was accessible 

 from the outside through an opening in the front of the 

 box. It had to be lifted to a height of 1.5 inches (an angle 

 of about 30). 



Box XX (bar outside) was about 13 by 11 by 10 inches 

 with a door 7 by 8 on the left side of the front. The door 



