The Mental Life of the Monkeys 181 



which held in a catch at its top. This nail was fastened 

 to a wooden knob (i by 5 by .375) which lay in a depression 

 at the top of the box. Only when the bolt had been 

 drawn and the plug and knob pulled, could the door be 

 opened. 



Box Gamma (wind) was 10 by 10 by 13 inches with its 

 door held by a wire fastened at the top and wound three 

 times about a screw eye in the top of the box. By unwind- 

 ing the wire the door could be opened. 



Box Delta (push back) was 12 by n by 10 inches. Its 

 door was held by a wooden bar projecting from the right 

 two inches in front of it. This bar was so arranged that 

 it could be pushed or pulled toward the right, allowing the 

 door to fall open. It could not be swung up or down. 



Box Epsilon (lever or push down) was 12 by 9 by 5 inches. 

 At the right side of its front was a hole J inch broad by ij 

 inches up and down. Across this hole on the inside of the 

 box was a strip of brass, the end of one bar of a lever. If 

 this strip was depressed \ of an inch, the door at the extreme 

 left would be opened by a spring. 



Box Zeta (side plug) was 12 by n by 10 inches. Its door 

 was held by a round bar of wood put through a hoop of 

 steel at the left side of the box. This bar was loose and 

 could easily be pulled out, allowing the door to be opened. 



Box Theta was the same as KK except that the door 

 could be opened as soon as the bolt alone was pulled or 

 pushed up. 



Box Eta was like Alpha save that the object at the back 

 of the box to be pulled was a brass ring. 



Apparatus QQ (chute) consisted of a lever mechanism so 

 arranged that by pushing in a bar of wood I to J an inch, 

 a piece of banana would be thrown down a chute into the 

 cage. The apparatus was placed outside the cage in such a 



