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 16 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 
to by 13 with a door 3 by 8.5 at the left side. The door 
could be opened only after (1) 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 11 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 catchon 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 1 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 
ro by 10 by 13 inches. 
Box KK (triple; bolt, side plug, and knob) was a box 16 
by 9 by 11 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 
