EXPERIMENTS ON THE RABBIT 149 



partments, the animals could not have been guided by the smell 

 of the food in the box. If the same door were open in two suc- 

 cessive experiments, the rabbit might be guided by the smell 

 of food on the ground in front of the door, since the food was 

 usually pulled out to be eaten; or by the smell left from pre- 

 vious nosing of the edges of the door. Throughout the greater 

 part of the experiments, however, the open door was on alternate 

 sides in succeeding experiments. Thus the strongest smell of 

 food on the ground or of nosing on the door was regularly on 

 the wrong side; that is, the side that had been the correct side 

 in the preceding experiment. Further, when a given discrim- 

 ination began to be learned, the correct paper was naturally 

 pushed oftener than the wrong paper; and if the same pieces of 

 paper had been constantly used and shifted from one door to 

 the other, of course the correct piece of paper, which was the 

 red in the experiments with red and greys, would accumulate 

 more of the odor of being nosed than the wrong piece would. 

 Hence we were careful to use a fresh piece of red paper in each 

 test. After the lapse of a few days we used again papers that 

 had been previously employed ; from time to time entirely fresh 

 papers were cut, and as we never noticed that the use of per- 

 fectly fresh correct papers disturbed the rabbits in the least, 

 we concluded that the odor left by nosing on a paper was not 

 influencing their choice. Again, it is quite conceivable that to 

 a rabbit the different papers used had different intrinsic odors. 

 That this was not a factor of any importance in determining 

 the behavior of our subjects we demonstrated in the following 

 way . After two of the rabbits (Light Nose and Dark Nose) had 

 been in training for twenty-eight days, four tests being given 

 each rabbit a day, a horizontal slit about 5 mm. wide and 10 

 cm. long was cut in both the red and grey papers at about the 

 level where the rabbit's nose touched them in pushing the doors. 

 Under this slit in the red paper was placed a piece of the grey 

 paper, and vice versa. If the animals had been guided by the 

 differing smells of red and grey paper, they must have been some- 

 what disturbed by an arrangement which brought the grey paper 

 smell in contact with their noses on the red door. The arrange- 

 ment made no striking change in the appearance of the two 

 doors. Neither of the rabbits was at all influenced by the new 

 state of affairs; both made equally good records before and 



