METHODS OF EXHIBITING REACTIVE TENDENCIES 



21 



All doors should slide vertically, upward, in wooden ways. 

 These are conveniently made by nailing strips of wood to the 

 side walls of the box. The strips serve the additional purpose 

 of supporting the side walls. The outside strip may either be 

 nailed to the end of the side wall or along the side. If nailed 

 to the end, it serves as the outside strip for adjacent doors and 

 thus reduces the amount of labor. In figure 2, the outside strip 

 for the entrance door is shown as nailed to the end of the side 

 wall. The writer prefers this method of construction. 



The reward receptacle, or mechanism, must be so constructed 

 as to be concealed when the exit doors are down and fully ex- 

 posed when they are raised. It may be simply and conveniently 

 constructed by nailing outside the rear end of each box a block 

 of wood, of the dimensions suggested in the table, in the center 

 of which there is a hole large enough to receive a metal food 

 cup. Aluminum is preferable as material for the food cup, and 

 desirable dimensions for the various sizes of apparatus are sug- 

 gested in table 1. In the proper position on the outside of the 

 exit door, there should be screwed a metal plate, bent at right 

 angles in such wise as to cover completely and tightly the food 

 cup when the exit door is down. This is shown in figure 4. 



Figure 4. — Metal cover for food cup. w, position of food cup under cover; z, point 

 at which cover is bent nearly at right angles; x, portion of cover which is at- 

 tached to exit door by means of wood screws, holes for which are indicated; 

 y, portion of cover which hides food cup. 



The dimensions for this cover or cap for the food cup, also, 

 are indicated in table 1. For the small apparatus, heavy tin 

 is a satisfactory material for this cover; for the medium appa- 

 ratus, light galvanized iron suffices; and for the- large appa- 

 ratus, it is necessary to use galvanized iron which is so thick 

 that the large apes cannot readily bend the cover out of shape. 

 The thickness should be about 1/16 inch. 



