180 Animal Intelligence 



was held in place by a bar swinging on a nail at the top, 

 with its other end resting in a latch at the left side of the 

 box. By pushing this up through an angle of 45 the door 

 could be opened. 



Box YY (push bar) was a box 1 6 by 8 by 12 inches with 

 a door at the left of its front. The door was held by a brass 

 bar which swung down in front of an L-shaped piece of 

 steel fastened to the inside of the door. This brass bar 

 was hung on a pivot at its center and the other end at- 

 tached to a bar of wood ; the other end of this bar projected 

 through a hole at the right side of the box. By pushing 

 this bar in about an inch the door could be opened. 



Box LL (triple ; nail plug, hook and bar) was a box 10 by 

 10 by 13 with a door 3 by 8.5 at the left side. The door 

 could be opened only after (i) a nail plug had been removed 

 from a hole in the back of the top of the box as in TT, (2) a 

 hook in the door had been unhooked, and (3) a bar on the 

 left side had been turned from a horizontal to a vertical 

 position. 



Box Alpha (catch at back) was n by 10 by 15 with the 

 door (4 by 4) in the left side of its front. The door was held 

 by a bolt, which, when let down, held in a catch on the inside 

 of the door. A string fastened to the bolt ran across to 

 the back of the box and through a hole to the outside. 

 There it ended in a piece of wood 2.5 by i by .25 inches. 

 When this piece of wood was pulled, the bolt went up and 

 the door fell open. 



Box Beta was the same as NN except in size. It was 

 10 by 10 by 13 inches. 



Box KK (triple ; bolt, side plug, and knob) was a box 16 

 by 9 by n with a door at the left side of the front. The 

 door was held by a bolt on the right side, a wooden plug 

 stuck through a hole in the box on its left side and a nail 



