68 HAROLD C. BINGHAM 



It' the form of the two end stimulus areas is square, and that 

 of the middle one is circular, a movement of the adapter to the 

 1. ft produces the condition shown in figure i. The stimulus I, 

 at the right is a square and that, n, at the left is a circle. But 

 when the shifter is moved to the right and the relative posi- 

 tions of the two forms with respect to each other become re- 

 versed since the square at the extreme left (now invisible) will 

 take the place of the circle, the circle will move over to the 

 place now occupied by the square, while the present square will 

 be shifted to the extreme right and will become invisible. 



This brief account of the apparatus as a whole should make 

 it ] possible to grasp more easily the details of the various sec- 

 tions. An understanding of the construction and use of the 

 mechanism will be made less difficult if the details are now con- 

 sidered in connection with each general part. 



i. Experiment box 



An illustration of the experiment box appears as figure 2. 

 This section of the apparatus is made of one-half inch lumber, 

 (except where stated otherwise), and is painted within and 

 without a dead black. It consists of four main parts: (1) A 

 is an entrance chamber, i5^X20X22. 2 The floor of A is pro- 

 vided with a metal tray containing a piece of wet felt which 

 fits the floor of the chamber. The entrance box may be re- 

 moved by raising out of the iron straps, C and C, the board 

 to which it is attached. (2) B is a discrimination chamber, 

 26 x 51 x 22. Leading from A to B is an entrance, I, 8x10. 

 The floor of B, like that of A, is carpeted with wet felt. The 

 tray of either compartment can be easily removed and cleaned. 

 I 3 ■ W and W are electric boxes separated from each other by 

 the partition 1). On the floors of W and W are fitted pieces 

 of slate, i6|x24f xi, carrying electric wires by means of 

 which an animal can be shocked when its behavior demands 

 punishment. By means of the interposited sides, OOO, the 

 trie compartments are set back 14 cm. from the stimulus 

 The floor of this extended portion drops down about 

 10 cm. below that of W-W. The middle O stands up closely 

 to the ada pter so that the exposed stimuli are set off from each 



I alesa otherwise stated, dimensions are given in centimeters and the order 

 ol presentation is length, width, and depth— inside measurements. 



