56 Animal Intelligence 
again and again in the course of this book to defend some 
theory, dubious enough to my own mind, in the hope of 
thereby inducing some one to oppose me and in opposing 
me to make the experiments I have myself had no oppor- 
tunity to make yet. Probably there will be enough op- 
position if I confine myself to the theories I feel sure of. 
EXPERIMENTS WITH Docs 
The boxes used were as follows: 
AA was similar to A (O at front), except that the loop was 
of stiff cord § inch in diameter and was larger (34 inches 
diameter) ; also it was hung a foot from the floor and 8 
inches to the right of the door. The box itself was 41 X 20 
X 23. 
BB was similar to B, the loop being the same as in AA, 
and being hung a foot from the floor. The box was of the 
same size and shape as AA. 
BBr was like BB, but the loop was hung 18 inches from 
the floor. 
CC was similar to C (button), but the button was 6 
inches long, and the box was 363 X 22 X 23. 
II was similar to I, but the box was 30 X 20 X 25 inches; 
the door (11 inches wide, 6 high) was in the left front corner, 
and the lever was 6 inches long and entered the box at a 
point 2 inches to the right of the door and 4 inches above 
the floor. 
In M the same box as in II was used, but instead of a 
lever projecting inside the box, a lever running outside 
parallel to the plane of the front of the box and 18 inches 
long was used. This lay close against the bars compos- 
ing the front of the box, and could be pawed down by 
sticking the paw out an inch or so between two bars, at 
