LOCALIZATION OF SOUND IN THE WHITE RAT 305 



to localize during the continuance of the remainder of the stim- 

 ulus. The same response was made when the fork was dampened 

 and the thud of striking only was given. 



It is worth while noting that the pitch in control IV was the 

 same as the predominant pitch in control III. The intensities 

 also were as close to equality as possible. Results 9 secured 

 on the rat's ability to discriminate intensities of tone would 

 suggest a very poor sensitivity to intensity differences. As a 

 result of these relations, a further question arises in regard to 

 the physiological basis for the perception of noise and the per- 

 ception of tone. 10 The fact that a tone 256 d. v. is ignored while 

 a noise 256 d. v. is reacted to accurately may indicate a separate 

 basis for the two perceptions (or, as stated above, in the light 

 of other work it may be due to deafness to tones of a certain 

 pitch). The problem must be carried much further, of course, 

 before definite conclusions can be drawn. 



(Con. V) In order to test the interrupted character of the 

 stimulus as a predominant factor in governing accuracy of 

 response, 256 d. v., on an organ pipe was tooted. Although 

 this too was of the same pitch as the tapping stimulus in control 

 III and was a klang and not a simple tone, the accuracy of 

 response was just as disturbed as with control IV. The responses 

 seem to have been made by chance, for there was much aimless 

 wandering and apparently no attention was paid to the sound 

 in the great majority of cases. The reasons for the breakdown 

 of the reactions may be either (1) inability to hear the tone 

 256 d. v. no matter whether simple or complex or (2) the fact 

 that the stimulus was too different from the standard stimulus 

 to be recognized. It must be noted, however, that the inter- 

 rupted character of this stimulus elicited no better response 

 than the continuous tone of the tuning fork while the tapping 

 on the resonator box gave normal results. This is again in 

 strict harmony with the results obtained by Dr. Hunter in his 

 work (p. 221) on the auditory sensitivity of the white rat above 

 referred to. 



(Con. VI) This control, further questioned the interrupted 

 character of the stimulus as the primary factor. The stimulus 

 used was hissing through the teeth, a continuous sound. The 



9 Hunter, the last article cited, pp. 219-20. 



10 Nagel's Handbuch der Physiol, der Menschen, Bd. 3, S. 585, 1905. 



