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JOSEPH U. YARBROUGH 



outset I was compelled to cover the entire apparatus, as the 

 cats were free to jump out at will. The wire used for this pur- 

 pose was of \" mesh and its tendency to blurr the field of vision 

 made it still more necessary that the white sawdust be used. 



Fig. 2 should give a clear presentation of the essentials of the 

 box when taken in connection with Fig. 1. 



Figure 2 



The cats on sound used the same apparatus as those on light, 

 the only difference being the change in stimulus. On the switch- 

 board B, Fig. 1, were placed three buttons which corresponded 

 to each of the three light boxes, a, b, and c. In each of these 

 boxes a buzzer was suspended directly over the door and 12" 

 from the floor of the apparatus. These buzzers were suspended 

 by a coiled wire, and were not in contact with the apparatus. 

 The system of wiring was the same as that of lighting — i.e., any 

 buzzer could be sounded at the wish of the experimenter by 

 pushing the proper button on the switchboard B. Such an 

 arrangement made it possible for the experiments on both sound 

 and light to be carried on without any interference. So far as 

 the knowledge of the experimenter goes, the cats on light never 

 found the buzzers, nor did the cats on sound find the lamps. 



The general method of experimentation was as follows: The 

 animal to be tested was put in the release box which is 



