AUDITORY SENSITIVITY OF THE WHITE RAT 319 



Controls — The following is a summary statement of the eleven 

 controls used in analyzing the animals' reactions: 



1. Leave off end-stops. Everything else normal. 



2. Do not sound whistle. Everything else normal. Re- 

 actions correct if they fit the series. 



3. Whistle is blown so as to give "rush of air sound" but no 

 tone. The "rush of air sound" is probably twice as loud as 

 it is when it accompanies the whistle tone. All else is normal. 



4. Make "rush of air sound" with lips. Intensity equal to 

 that of control 3. Care taken that air currents do not reach rats. 



5. Clap hands in place of giving whistle tone. Medium 

 intensity. 



6. Two holes are bored in wall of room. A rubber tube 

 passes through one from the experimenter to a Galton whistle 

 placed in the adjoining room. The mouth of the whistle is set 

 close in front of the second hole with a paper reflector directing 

 the sound back into the experiment room. The whistle is set 

 for the tone 3906.17 d.v. and is sounded in place of the whistle 

 over the apparatus box. Everything else is normal. 



7. Whistle over the apparatus box is used at the same in- 

 tensity as the tone of control 6. The two were matched by 

 sounding first one and then the other. The pressure in the 

 water manometer was 4 cm. 



8. Fork 1280 d.v. sounded in place of whistle and at a little 

 more than the intensity of control 7. 



9. The whistle over the apparatus box set at 1280 d.v. and 

 sounded under normal conditions. 



10. Fork 1152 d.v. and fork 1280 sounded as a chord in place 

 of normal whistle tone. Slightly greater intensity than control 8. 



11. The whistle used in control 6 was substituted for the 

 whistle usually sounded over the box. The normal intensity 

 and pitch were given. 



Inasmuch as I regard the full presentation of the records 

 on these controls as a matter of great importance, tables 5, 6 

 and 7. are given in the appendix. In these the reader will find 

 a chronological statement of controls and results for each of 

 the three rats. Here in the body of the paper, I shall gather 

 together all of the tests made upon a given control irrespective 

 of the relative times at which the tests were made. 



