

The Sense of Sight: Brightness Vision 93 



:ests. Figure 15 is its ground plan. This box, which was 

 made of wood, was 98 cm. long, 38 cm. wide, and 17 cm. 

 deep, as measured on the outside. 

 The plan of construction and its 

 significance in connection with 

 these experiments on vision will 

 be clear from the following ac- 

 count of the experimental 

 procedure. A mouse whose 

 brightness vision was to be 

 tested was placed in the 

 nest-box, A (Figure 15). 

 Thence by pushing open 

 the swinging door at /, it 

 could pass into the en- 

 trance chamber, B. 

 Having entered B it 

 could return to A only 

 by passing through 

 one of the electric- 

 boxes, marked W, 

 'and following the 

 alley to O, where by 

 pushing open the 

 swing door it could 

 enter the nest-box. 



FIGURE 15. Ground plan of discrimination 

 box. A, nest-box; B, entrance chamber; W,W, 

 electric-boxes; L, doorway of left electric-box; R, 



The door at 7 SWUng doorwayof righ t electric-box; E, exit from electric- 

 inward, toward B, box to alley; I, swinging door between A and; 

 1 ,1 , ^ O, swinging door between alley and A ; 1C, induc- 

 U > tion apparatus; C, electric cell; K, key in circuit. 



right and left, swung 



outward, toward A, only. It was therefore impossible for 

 the mouse to follow any other course than A-I-B-L-W-E-O 

 or A-I-B-R-W-E-O. The doors at / and O were pieces of 



