54 



STELLA BURNHAM VINCENT 



open by the animal's nose from the runways but which could 

 not be opened by it from the food box. A button secured the 

 doors when it was desired to have them closed. Later, when 

 it became necessary, copper plates nine inches in length were 

 screwed to the floor of the alleys at the food box end and con- 

 nected by wires across the top of the food box with key, induc- 

 tion coil and batteries. The box had a glass cover in two parts 

 but as the animals became more accustomed to the experiment 

 it was not needed. 



Fig. 12 — Top view of problem box. The wiring is arranged so that the current 

 may be turned on to any two of the plates leaving the third one safe. 



B. General Conduct of the Experimentation 



The box was kept thoroughly clean, was washed with disin- 

 fectants to exclude odor and, in order to prevent choice by 

 position, the partitions were changed so that the corrugated 

 pathway recurred regularly in the following serial order: — C, B, 

 C, A, B, C, A, C, B, A, B, B, C, C, A, A, B, A, A, C, A, B, C, C, 

 B, B, A, B, C. 



The rats were put in the center of the entrance box with 

 their faces away from the openings of the alleys so that they 



