Hamilton, Unusual Reactiou of a Dog. 



ii^ 



By hooking a given string to the trigger the pedal from which it 

 came was thus attached to the door-release. (5) Four "pedal 

 cards" [F), which were simply heavy wooden boards, 4 inches 

 wide by 11 inches high; they were furnished with two legs each, 

 which fitted into slanting holes in the pedals in such a manner as 

 to give them an upright position when in place. Each pedal card 

 had a different colored paper pasted upon its anterior surface, 

 viz: black, red, green and yellow. (6) Four pairs of odor cards 

 (G); these w^ere small wooden paddles with cotton tacked to their 



*-«B 



Fig. I. Diagram of the experiment cage; A, spring door; jB, button with trigger string attached; C, 

 trigger with one pedal string attached; DDDD, pedals, one of which is shown separately with string 

 and suspension spring; £, sign board; FFi<'F, pedal cards, one of which is shown separately, with legs 

 to fit into the holes in the pedals, and with odor card (G) suspended from its anterior surface. 



anterior surfaces. Each of these was kept saturated with a drug 

 having a distinctive odor, viz: asafcetida, lupulin, castor oil and 

 beef extract. (7) Four wooden sign boards (£), 11 inches wide, 

 3 feet long. Their anterior surfaces were covered with papers 

 matching in color those of the cards. (8) One white sign board 

 and pedal card, and three plain pedal cards. 



Experiments with the luhite sign board and ivhite pedal card. — 

 In this series of experiments the different pedals were attached, 

 one at a time, and in varying order, to the trigger, the attached 

 pedal always bearing the white pedal card, and the unattached 



