EXPERIMENTS ON THE RABBIT 



147 



cated and costly, it is, as Yerkes and Watson themselves admit,' 

 worth while to attempt preliminary work under simpler condi- 

 tions. Certain sources of error, other than the impurity of the 

 colors, pointed out by Watson as involved in the employment of 

 colored papers, we have, as will be indicated, avoided by slight 

 modifications of our method. Figure i shows the reflective 

 power of the colored papers used, measured by means of a 

 MgO screen. Curve A indicates that of the Bradley saturated 

 blue paper; curve B that of the fresh Bradley saturated red 

 paper, and curve C that of the Bradley saturated red paper 

 somewhat darkened by time. The tests of the red paper were 

 made through the kindness of Professor Herbert E. Ives of 

 Cleveland. 



Figure 2. Color vision apparatus for 

 testing rabbit. Doors closed. 



Figure 3. 



Same, showing rabbit 

 opening door. 



Our apparatus consisted of a wooden box, 24 inches long by 

 13 inches deep and 13 inches high, divided into two equal com- 

 partments by an inside partition. Each of these two compart- 

 ments opened by a door pivoted so as to swing on a horizontal 

 axis; the two doors appeare;] side by side when the box was 

 viewed from the front. They were 9 inches high by 4! inches 

 wide. Each door could be fastened on the inside by a button. 

 The lid of the box was hinged so that food could be put in and 

 the doors fastened and unfastened between experiments. On 

 one of the doors was tacked with thumb-tacks a piece of Brad- 

 ley saturated red paper, somewhat smaller than the door; to 

 the other door was tacked a piece of Hering gray paper of the 

 same size and shape as the red paper. Food was placed in both 



3 Yerkes, R. M., and Watson, J. B. Methods of Studying Vision in Animals. 

 Behavior Monographs, vol. I, no. 2. 1911. 



