34 HARRY MILES JOHNSON 



is to be released. G and G' are two punishment-grills — strips 

 of brass about 3' long, secured to a white pine board 3' x 2' . 

 Alternate strips are connected with the respective poles 

 of the secondary coil of an inductorium, leaving the other 

 end free. When the current is switched in, the animal's 

 foot must rest on two or more of these strips, which are 

 onlyi cm. wide and i cm. apart, thus completing the circuit 

 and causing the animal to receive a shock. The induc- 

 torium should be placed outside the room in which the animal 

 is being worked, and far enough away that the sparking noise 

 will not disturb the experiment. The cuiTcnt may be shifted 

 through G or G' by a double -throw switch at the operator's 

 station. My experience showed that in a cage of this size the 

 grills G and G' should be made longer than three feet ; six feet 

 would be much better. Some of the dogs used in these experi- 

 ments would jump over the grill when they were shocked, in- 

 stead of turning back. They probabl}^ would not have persisted 

 in this attempt had the distance been greater. As it was, addi- 

 tional rods had to be run from side to side of alleys D and D^ 

 above the grills, so that the dogs could not jump over them and 

 escape punishment. 



The frame-work of this cage is constructed of yellow pine, 

 i''x3'^ the top and sides are covered with woven steel wire, 

 having a mesh about i cm. square. Food is kept in both the 

 food-compartments F and F'. The animal is given the problem 

 of choosing a turn to the left into alley D, leading to food- 

 compartment F, at one tone, and a turn to the right into alley 

 D', leading to food-box F', at the other tone. The stimulus- 

 tone may be struck while the animal is in the home-box A, and 

 the animal released after it has been damped ; or the tone may 

 be sounded after the animal's release, say one-half second before 

 he can reach the end of the introductory alley. If punishment 

 is to be administered, the animal receives it instantly he makes 

 the WTong turn. 



In a part of the writer's experiments presently, to be des- 

 cribed the experimenter sat at a table about four feet from 

 door V of the home-box. When the animals should have begun 

 to discriminate a screen could be inteqoosed between the table 

 and the cage to conceal the operator. Later the entire appa- 



