32 Animal Intelligence 
D. The door was in the extreme right of the front. 
A string fastened to the bolt which held it ran up 
over a pulley on the top edge and back to the top edge 
of the back side of the box (3 inches in from the right 
side) and was there firmly fastened. The top of the box 
was of wire screening and arched over the string } inch . 
above it along its entire length. A slight pull on the 
string anywhere opened the door. This box was 20 x 16, 
but a space 7 X 16 was partitioned off at the left by a wire 
screen. D may be called ‘String.’ 
D1 was the same box as B, but had the string fastened 
firmly at the back instead of running over a pulley and 
ending in a wire loop. We may call it ‘String 2d.’ 
E. A string ran from the bolt holding the door up over a 
pulley and down to the floor outside the box, where it was 
fastened 2 inches in front of the box and 14 inches to the 
left of the door (looking from the inside). By poking a paw 
out between the bars and pulling this string inward the door 
would be opened. We may call E ‘String outside.’ 
In F the string was not fastened to the floor but ended ina 
loop 23 inches in diandeter-which could be clawed down so as 
toopen the door. Unless the pull was in just the right direc- 
tion, the string was likely to catch on the pulley. This loop 
hung 3 inches above the floor, and 13 inches in front of the 
box. We may call F ‘String outside unfastened.’ 
G was a box 29 X 203 X 224, with a door 29 x 12 hinged - 
on the left side of the box (looking from within), and kept 
closed by an ordinary thumb latch placed 15 inches from 
the floor. The remainder of the front of the box was closed 
in by wooden bars. The door was a wooden frame covered 
with screening. It was not arranged so as to open as soon as 
the latch was lifted, but required a force of 400 grams, even 
when applied to the best advantage. The bar of the thumb 
